Post by thread:[EE]: Solid state relay difficulty

Hi all, I'm using an Omron G3MB-202P solid state relay, 5V flavor. It's a phototriac. It's not behaving how I would expect though, hopefully someone can clear this up.. Pin definitions: 1 - load 2 - load 3 - (+) input 4 - (-) input Here's what I am seeing: Connections: to test this I just want to light an LED... 5V to Anode of 5V LED pin 1 - cathode of LED pin 2 - ground pin 3 - ground pin 4 - ground This is how I start it up. Now when I apply power to this, of course nothing happens as I expect. I then switch over the pin 3 to +5V, the LED lights, as expected, I then switch the pin 3 back to ground, the led stays lit. In fact, no arrangement of the input pins (3,4) will make the damn LED shut off, I can't break the circuit once it's made... Doesn't sound too useful of a relay! Hopefully I'm doing something obviously wrong!! I've tried this with 3 different relays so I doubt they are defective... Someone please smack me and tell me the simple solution! :) Thanks all! -- Nick spam_OUTnickTakeThisOuTveys.com | http://www.veys.com/nick -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

It seems you don't know how a thyristor or a triac works. If you supply A-K ( thyristor ) or A1-A2 ( triac ) ( A = anode, K = cathode ) in DC the AK or A1-A2 junction will stay on after a gate or opto command until the currrent through this junction will go to zero ( in fact must be less than sustain current) and this will never hapened in DC . Use a bulb for test and supply it in AC. Will works. Cheers, Vasile On Thu, 2 Aug 2001, Nick Veys wrote: {Quote hidden}> Hi all, I'm using an Omron G3MB-202P solid state relay, 5V flavor. It's > a phototriac. It's not behaving how I would expect though, hopefully > someone can clear this up.. > > Pin definitions: > > 1 - load > 2 - load > 3 - (+) input > 4 - (-) input > > Here's what I am seeing: > > Connections: to test this I just want to light an LED... > > 5V to Anode of 5V LED > pin 1 - cathode of LED > pin 2 - ground > pin 3 - ground > pin 4 - ground > > This is how I start it up. > > Now when I apply power to this, of course nothing happens as I expect. > I then switch over the pin 3 to +5V, the LED lights, as expected, I then > switch the pin 3 back to ground, the led stays lit. In fact, no > arrangement of the input pins (3,4) will make the damn LED shut off, I > can't break the circuit once it's made... Doesn't sound too useful of a > relay! > > Hopefully I'm doing something obviously wrong!! > > I've tried this with 3 different relays so I doubt they are defective... > > Someone please smack me and tell me the simple solution! :) > > Thanks all! > > -- Nick > > .....nickKILLspam@spam@veys.com | http://www.veys.com/nick > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Nick, The phototriac is intended to switch high voltage AC currents from a low voltage DC source and to provide dielectric isolation (7,500V insulation) between the DC and AC sources. As per the pin out that you provided: Pin 3 is the anode of the phototriac's internal LED. A DC current (+) of 10mA to 25 mA should be applied to pin 3 to illuminate the internal LED and to turn on the triac. Pin 4 is the cathode of the phototriac's internal LED and is frequently connected to the DC power supply's common (-). Pin 1 is typically connected to the AC load. The other end of the AC load is connected directly to the AC power source (excluding fuses/circuit breakers). Pin 2 is connected to the AC common. A true test of the triac's performance requires an AC power source, an AC load and a low voltage DC power source. However, a crude basic functional test may be performed using DC. While not intended, nor conventional, the triac may be used for certain DC applications, however, generally there are more appropriate DC devices. Vasile, A triac will turn off or interrupt DC current, if the DC current is pulsed energy and decreases in amplitude to near zero volts. As an example, a triac will effectively control a half wave or full wave rectified DC signal. However, an SCR would be a more appropriate control device. Good Luck! Sincerely, Ned Seith Nedtronics 59 3rd Street Gilroy, CA 95020 (408) 842-0858 At 09:22 AM 8/2/01 +0300, you wrote: {Quote hidden}>It seems you don't know how a thyristor or a triac works. >If you supply A-K ( thyristor ) or A1-A2 ( triac ) ( A = anode, K = >cathode ) in DC the AK or A1-A2 junction will stay on after a gate or opto >command until the currrent through this junction will go to zero ( in fact >must be less than sustain current) and this will never hapened in DC . >Use a bulb for test and supply it in AC. Will works. >Cheers, Vasile > > >On Thu, 2 Aug 2001, Nick Veys wrote: > > > Hi all, I'm using an Omron G3MB-202P solid state relay, 5V flavor. It's > > a phototriac. It's not behaving how I would expect though, hopefully > > someone can clear this up.. > > > > Pin definitions: > > > > 1 - load > > 2 - load > > 3 - (+) input > > 4 - (-) input > > > > Here's what I am seeing: > > > > Connections: to test this I just want to light an LED... > > > > 5V to Anode of 5V LED > > pin 1 - cathode of LED > > pin 2 - ground > > pin 3 - ground > > pin 4 - ground > > > > This is how I start it up. > > > > Now when I apply power to this, of course nothing happens as I expect. > > I then switch over the pin 3 to +5V, the LED lights, as expected, I then > > switch the pin 3 back to ground, the led stays lit. In fact, no > > arrangement of the input pins (3,4) will make the damn LED shut off, I > > can't break the circuit once it's made... Doesn't sound too useful of a > > relay! > > > > Hopefully I'm doing something obviously wrong!! > > > > I've tried this with 3 different relays so I doubt they are defective... > > > > Someone please smack me and tell me the simple solution! :) > > > > Thanks all! > > > > -- Nick > > > > nickKILLspamveys.com | http://www.veys.com/nick > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Thu, 2 Aug 2001, Ned Seith wrote: > > Vasile, > > A triac will turn off or interrupt DC current, if the DC current is pulsed > energy and decreases in amplitude to near zero volts. Do I said something else ? If the current flowing from A to K is less than sustaining current then will shut off. This current may be near zero or greatest, depends on device. Power devices have greatest sustaining current. GTO are better for DC usage, they haven't this ill, but are difficult to command. Cheers to you, too ! Vasile {Quote hidden}> > At 09:22 AM 8/2/01 +0300, you wrote: > >It seems you don't know how a thyristor or a triac works. > >If you supply A-K ( thyristor ) or A1-A2 ( triac ) ( A = anode, K = > >cathode ) in DC the AK or A1-A2 junction will stay on after a gate or opto > >command until the currrent through this junction will go to zero ( in fact > >must be less than sustain current) and this will never hapened in DC . > >Use a bulb for test and supply it in AC. Will works. > >Cheers, Vasile > > > > > >On Thu, 2 Aug 2001, Nick Veys wrote: > > > > > Hi all, I'm using an Omron G3MB-202P solid state relay, 5V flavor. It's > > > a phototriac. It's not behaving how I would expect though, hopefully > > > someone can clear this up.. > > > > > > Pin definitions: > > > > > > 1 - load > > > 2 - load > > > 3 - (+) input > > > 4 - (-) input > > > > > > Here's what I am seeing: > > > > > > Connections: to test this I just want to light an LED... > > > > > > 5V to Anode of 5V LED > > > pin 1 - cathode of LED > > > pin 2 - ground > > > pin 3 - ground > > > pin 4 - ground > > > > > > This is how I start it up. > > > > > > Now when I apply power to this, of course nothing happens as I expect. > > > I then switch over the pin 3 to +5V, the LED lights, as expected, I then > > > switch the pin 3 back to ground, the led stays lit. In fact, no > > > arrangement of the input pins (3,4) will make the damn LED shut off, I > > > can't break the circuit once it's made... Doesn't sound too useful of a > > > relay! > > > > > > Hopefully I'm doing something obviously wrong!! > > > > > > I've tried this with 3 different relays so I doubt they are defective... > > > > > > Someone please smack me and tell me the simple solution! :) > > > > > > Thanks all! > > > > > > -- Nick > > > > > > .....nickKILLspam.....veys.com | http://www.veys.com/nick > > > > > > -- > > > http://www.piclist.com hint: The PICList is archived three different > > > ways. See http://www.piclist.com/#archives for details. > > > > > > > > > >-- > >http://www.piclist.com hint: The PICList is archived three different > >ways. See http://www.piclist.com/#archives for details. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

If it's a triac device it will only work on AC, as the triac will stay conducting until the current crosses zero. On Thu, 2 Aug 2001 01:47:31 -0500, you wrote: {Quote hidden}>Hi all, I'm using an Omron G3MB-202P solid state relay, 5V flavor. It's >a phototriac. It's not behaving how I would expect though, hopefully >someone can clear this up.. > >Pin definitions: > >1 - load >2 - load >3 - (+) input >4 - (-) input > >Here's what I am seeing: > >Connections: to test this I just want to light an LED... > >5V to Anode of 5V LED >pin 1 - cathode of LED >pin 2 - ground >pin 3 - ground >pin 4 - ground > >This is how I start it up. > >Now when I apply power to this, of course nothing happens as I expect. >I then switch over the pin 3 to +5V, the LED lights, as expected, I then >switch the pin 3 back to ground, the led stays lit. In fact, no >arrangement of the input pins (3,4) will make the damn LED shut off, I >can't break the circuit once it's made... Doesn't sound too useful of a >relay! > >Hopefully I'm doing something obviously wrong!! > >I've tried this with 3 different relays so I doubt they are defective... > >Someone please smack me and tell me the simple solution! :) > >Thanks all! > >-- Nick > >EraseMEnickspam_OUTTakeThisOuTveys.com | http://www.veys.com/nick -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Sergi, Vasili's statement that "this will never hapened in DC" suggests that a triac would not turn off while conducting DC current. When the DC current of a half or full wave rectified DC signal diminishes below the holding current of the triac, the triac will shut off, if a gate signal is not present. The DC current of a half or full wave rectified DC signal is a proportional by product of the DC voltage. If the load was purely resistive, then the DC voltage and the DC current would reach zero at the same moment. However, as you have "correctly" indicated, if the load is inductive (or capacitive) there will be a phase shift between the DC voltage and DC current. However, the fact remains that a triac will turn off when conducting the DC current of a half or full wave rectified signal. When I attended school nearly 40 years ago, half wave and full wave rectified signals were referred to as "pulsed DC energy" and our fellow classmates were never referred to as "dear". How times have changed Sincerely, Ned Seith Nedtronics 59 3rd Street Gilroy, CA 95020 (408) 842-0858 . At 11:32 AM 8/2/01 +0200, you wrote: {Quote hidden}> > A triac will turn off or interrupt DC current, if the DC > > current is pulsed > > energy and decreases in amplitude to near zero volts. As an example, a > > triac will effectively control a half wave or full wave > > rectified DC signal. > >Dear, formally a 'DC PULSE' is an AC signal plus a DC bias. And Vasili >explains CLEAR the physics of a triac. Tiacs CUT-OFF in absence of current, >not where DC voltage nears zero (remember inductive loads). > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 11:18 AM 8/2/01 +0100, you wrote: >If it's a triac device it will only work on AC, as the triac will stay >conducting until the current crosses zero. While this is correct there might be situations where you could use the behavior to advantage on DC. Shorting the output with a momentary switch (or interrupting the current) will turn it off ( assuming dv/dt isn't too high). So, for a security alarm powered from a 12VDC battery, it might be just what you want. Another possible use on DC would be as a cheap isolated way to control high voltage relatively low currents.. 10's of uA, say. With a high value series resistor between, say +300 and -300 VDC you could get an isolated 600V swing from your micro etc. with a very cheap little devices. This works because the current is less than the holding current (confirm this at maximum Ta). Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" speffspam_OUTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Sergi, I'm sure that you are quite knowledgeable and very capable. Disrespect was never intended. The way that I see it, is that anyone who posts to this list, has significant knowledge and/or experience which has contributed to them gravitating to this list. To the uninitiated, the contents of this list with the hardware, firmware, software and other technical references would be un-interpretable sending them off to the nearest prime time chat room. It's amazing to me that we have this virtual space where those individuals who are motivated by electronics, science and technology from around the entire world can gather, listen, observe, talk, share, debate, argue and occasionally throw rocks at each other. Sincerely, Ned Seith Nedtronics 59 3rd Street Gilroy, CA 95020 (408) 842-0858 At 03:25 PM 8/2/01 +0200, you wrote: {Quote hidden}>Mr. Steith, > >When I attented school nerly 25 years ago, I was (I think) so applied to the >fellow lessons in order to >remember now if they referred us as 'dear' or not. > >By the by, 15 years ago I was dessigning special needs triacs and srcs on >the National Microelectronics Center (Spain). So I think I know a little. > >Sincerely, >Sergi Sanchez > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Ok, first I want to thank everyone who replied to this... The responses make perfect sense, I picked the wrong part. I guess the next time I need to switch a light bulb, I'll be ready! Here is what I am trying to do. I have a shorting block I want to control from a PIC. I picked a relay since it's basically able to mimic a momentary pushbutton which is what I am trying to do. I assumed a "relay is a relay" so I thought a solid state relay would behave like any other relay, I was wrong! :) So basically I need some way to short a block momentarily, preferably without any additional hardware between it and the PIC (which is why I picked the previous relay, had 5V input, low low amperage to switch). Speed isn't a big issue, it needs to be able to switch on/off within ~500ms. If anyone can perhaps show me the "correct" solid state relay I would really appreciate it, as I don't want to just try again and see if I pick a DC one this time! :) Thanks again for all the answers! @spam@nickKILLspamveys.com | http://www.veys.com/nick > {Original Message removed}

Are you using this "relay" for braking? ----- Original Message ----- From: "Nick Veys" <KILLspamnickKILLspamVEYS.COM> To: <RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU> Sent: Thursday, August 02, 2001 7:26 AM Subject: Re: [EE]: Solid state relay difficulty {Quote hidden}> Ok, first I want to thank everyone who replied to this... The responses > make perfect sense, I picked the wrong part. I guess the next time I > need to switch a light bulb, I'll be ready! > > Here is what I am trying to do. > > I have a shorting block I want to control from a PIC. I picked a relay > since it's basically able to mimic a momentary pushbutton which is what > I am trying to do. I assumed a "relay is a relay" so I thought a solid > state relay would behave like any other relay, I was wrong! :) > > So basically I need some way to short a block momentarily, preferably > without any additional hardware between it and the PIC (which is why I > picked the previous relay, had 5V input, low low amperage to switch). > > Speed isn't a big issue, it needs to be able to switch on/off within > ~500ms. > > If anyone can perhaps show me the "correct" solid state relay I would > really appreciate it, as I don't want to just try again and see if I > pick a DC one this time! :) > > Thanks again for all the answers! > > spamBeGonenickspamBeGoneveys.com | http://www.veys.com/nick > > > > {Original Message removed}

I know it should be hard, hence my difficulty! :) Go figure! It's simply shorting two pins on a little fan controller I have made here, on the device it brings +5 to Ground to let it know to turn on but really, I don't want it to matter... I simple want something that will be switchable from: Open circuit -> Closed circuit -> Open circuit in 1/2 a second or so, nothing complex, nothing elaborate, simply like what a relay would do, only no real significant current (uA) or anything will flow though this so it doesn't need to be heavy duty at all! I'm looking at some Optoisolators and some seem like they might work, and I really like the idea of having 4 channels, that would simplify my PCB... But again I have no experience with those and don't know if they would work either... RemoveMEnickTakeThisOuTveys.com | http://www.veys.com/nick > {Original Message removed}

Nick Veys wrote: > > I know it should be hard, hence my difficulty! :) Go figure! > > It's simply shorting two pins on a little fan controller I have made > here, on the device it brings +5 to Ground to let it know to turn on but > really, I don't want it to matter... I simple want something that will > be switchable from: Open circuit -> Closed circuit -> Open circuit in > 1/2 a second or so, nothing complex, nothing elaborate, simply like what > a relay would do, only no real significant current (uA) or anything will > flow though this so it doesn't need to be heavy duty at all! > > I'm looking at some Optoisolators and some seem like they might work, > and I really like the idea of having 4 channels, that would simplify my > PCB... But again I have no experience with those and don't know if they > would work either... Have you considered a relay? A "real" relay that is! :o) Simple to drive with your PIC and should work your AC fan load ok since you say it is low power. -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Mike Mansheim wrote: > > > Have you considered a relay? A "real" relay that > > is! :o) Simple to drive with your PIC and should > > work your AC fan load ok since you say it is low > > power. > > Last time I went looking for a relay to run with a pic, > I ended up using a solid state relay because the > mechanical relays needed more drive current than the > pic could do directly. Of course, I limited my selection > to whatever was listed in Digikey. > So, does a solid state relay count as "real"? No. :o) Try using a real relay with the coil driven by a cheap 10 cent transistor like a BC337 or equiv, and a diode across the relay coil, this can give advantages over a solid state relay because of the total isolation of the relay contacts from the coil and PIC. Solid state relays are fine in many cases, but "real" relays have their place, and are good safe hardware for newbies. -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Hi Nick, At 1:19 PM -0500 8/2/01, Nick Veys wrote: >I know it should be hard, hence my difficulty! :) Go figure! > >It's simply shorting two pins on a little fan controller I have made >here, on the device it brings +5 to Ground to let it know to turn on If this is the case why not use a NPN transistor. Connect the control line through a limiting resistor to the base, emitter to ground and the pin to be switched to the collector ? >but >really, I don't want it to matter... I simple want something that will >be switchable from: Open circuit -> Closed circuit -> Open circuit in >1/2 a second or so, nothing complex, nothing elaborate, simply like what >a relay would do, only no real significant current (uA) or anything will >flow though this so it doesn't need to be heavy duty at all! > >I'm looking at some Optoisolators These are only necessary if you want to electrically isolate the control line from the controlled circuit. >and some seem like they might work, >and I really like the idea of having 4 channels, Multiple transistors can be had in a multi-pin DIP package, or since your switching 5v to gnd, with little current, you could use CMOS switches (a.k.a. transmission gates) such as the 4066, 4 switches/package. This may be a better choice since the inputs are logic compatible, so the limiting resistors can be eliminated. >that would simplify my >PCB... But again I have no experience with those and don't know if they >would work either... > >nickEraseME.....veys.com | http://www.veys.com/nick > Heinz -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Seems like your original idea would almost work, now if you could put a capacitor in series with it you'd get your "shorting" current briefly, then it would go away. Once it did the triac would reset. Make sure something bleeds the capacitor off between uses. Barry {Quote hidden}>It's simply shorting two pins on a little fan controller I have made >here, on the device it brings +5 to Ground to let it know to turn on but >really, I don't want it to matter... I simple want something that will >be switchable from: Open circuit -> Closed circuit -> Open circuit in >1/2 a second or so, nothing complex, nothing elaborate, simply like what >a relay would do, only no real significant current (uA) or anything will >flow though this so it doesn't need to be heavy duty at all! > >RemoveMEnickEraseMEEraseMEveys.com | http://www.veys.com/nick > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

part 1 3010 bytes content-type:text/plain; charset=us-ascii You can do this with a mosfet if you can bias it correctly. I have not seen your circuit, so I can't suggest any biasing solutions. You might be able to use something like a 4066 quad switch...... Scott F. Touchton 1550 Engineering Manager JDS Uniphase Nick Veys <RemoveMEnickspam_OUTKILLspamVEYS.COM To: RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU > cc: Sent by: pic Subject: Re: [EE]: Solid state relay difficulty microcontrolle r discussion list <PICLIST@MITVM A.MIT.EDU> 08/02/01 04:23 PM Please respond to pic microcontrolle r discussion list I think everyone is missing my point... I was hesistant to say I was connecting +5 to Gnd because then I would get the "use a transistor" message. And a real relay is great, but I don't like the extra hardware involved, I'm looking for something simple, all I'm doing is shorting leads! I would think there would be some kind of solid state relay that can do this but apparently not? EraseMEnickspamspamBeGoneveys.com | http://www.veys.com/nick > {Original Message removed} part 2 4336 bytes content-type:application/octet-stream; (decode) part 3 131 bytes -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Solid state relays will work, just as long as you get the right one. The relay you got used a triac, so once it was activated, it will stay on as long as you have current running through it. Get a relay that does not have an SCR or triac output an you should be fine. Also, I never saw solid state relays with this, but I might as well add this in just in case; make sure it is not a latching relay. Latching relays act like toggle switches, with an input for on, and an input for off. Once you activate the on/off state, it will remain in that state. --Nick --- Nick Veys <RemoveMEnickKILLspamVEYS.COM> wrote: {Quote hidden}> Ok, first I want to thank everyone who replied to > this... The responses > make perfect sense, I picked the wrong part. I > guess the next time I > need to switch a light bulb, I'll be ready! > > Here is what I am trying to do. > > I have a shorting block I want to control from a > PIC. I picked a relay > since it's basically able to mimic a momentary > pushbutton which is what > I am trying to do. I assumed a "relay is a relay" > so I thought a solid > state relay would behave like any other relay, I was > wrong! :) > > So basically I need some way to short a block > momentarily, preferably > without any additional hardware between it and the > PIC (which is why I > picked the previous relay, had 5V input, low low > amperage to switch). > > Speed isn't a big issue, it needs to be able to > switch on/off within > ~500ms. > > If anyone can perhaps show me the "correct" solid > state relay I would > really appreciate it, as I don't want to just try > again and see if I > pick a DC one this time! :) > > Thanks again for all the answers! > > nickSTOPspamspam_OUTveys.com | http://www.veys.com/nick > > > > {Original Message removed}

On Fri, 3 Aug 2001, Roman Black wrote: > Have you considered a relay? A "real" relay that > is! :o) Simple to drive with your PIC and should > work your AC fan load ok since you say it is low > power. > -Roman Roman, Nick, what do you say about this: One npn transistor driven in base through a resistence from pic, transistor will short circuit ( when is on ) the +/- section of one rectifying bridge, colector to +bridge pin, emiter to -bridge pin and GND of pic supply. In series with ~ bridge pin, the fan , the other fan pin and ~ pin of the bridge to AC. ( same configuration like those used for driving full AC load using thyristors but with transistors ) I think will work ok and will be better than a relay. Vasile -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

Yes Ned, you have right. Now I'm sure it was a language problem. There are some diferences using technical terminology in different countries. This make me seriously thinking that probably is better to keep my mouth shut on this list. BTW, when I said DC I was thinking exactly only to rectified and filtered DC. And of course a full or half rectified wave is also DC. It's important we both understood the problem ( me only 25 years ago...) I hope Nick too. Sincerely yours, Vasile On Thu, 2 Aug 2001, Ned Seith wrote: {Quote hidden}> Sergi, > > Vasili's statement that "this will never hapened in DC" suggests that a > triac would not turn off while conducting DC current. When the DC current > of a half or full wave rectified DC signal diminishes below the holding > current of the triac, the triac will shut off, if a gate signal is not > present. The DC current of a half or full wave rectified DC signal is a > proportional by product of the DC voltage. If the load was purely > resistive, then the DC voltage and the DC current would reach zero at the > same moment. However, as you have "correctly" indicated, if the load is > inductive (or capacitive) there will be a phase shift between the DC > voltage and DC current. However, the fact remains that a triac will turn > off when conducting the DC current of a half or full wave rectified signal. > When I attended school nearly 40 years ago, half wave and full wave > rectified signals were referred to as "pulsed DC energy" and our fellow > classmates were never referred to as "dear". How times have changed > > Sincerely, > Ned Seith > Nedtronics > 59 3rd Street > Gilroy, CA 95020 > (408) 842-0858 > . > At 11:32 AM 8/2/01 +0200, you wrote: > > > A triac will turn off or interrupt DC current, if the DC > > > current is pulsed > > > energy and decreases in amplitude to near zero volts. As an example, a > > > triac will effectively control a half wave or full wave > > > rectified DC signal. > > > >Dear, formally a 'DC PULSE' is an AC signal plus a DC bias. And Vasili > >explains CLEAR the physics of a triac. Tiacs CUT-OFF in absence of current, > >not where DC voltage nears zero (remember inductive loads). > > > >-- > >http://www.piclist.com hint: The PICList is archived three different > >ways. See http://www.piclist.com/#archives for details. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservEraseMEmitvma.mit.edu with SET PICList DIGEST in the body

Nick, I've done something like this before. But I've used it to control 230 Volts AC. I used MOC3041 Triac OptoCoupler with a BTA610 Triac to make a Solid State Relay. Triacs don't turn off even if you take the gate drive off. That is one of the greatest features of SCRs and Triacs. Sometimes this latching effect can come in quite handy. On AC, this makes no difference, unless you want to play with the AC waveform. If you really want to test out the Triac, use an AC voltage. If you turn on the triac and remove the drive, it will turn off in the next Zero Crossing of the AC line. SSRs are actually meant for switching AC. They are of little or no use on DC. To test the SSR, you may try connecting a small light bulb or something in series with the SSR and AC Line. Regards, Jeethu Rao > {Original Message removed}

Nick, for real low current, and if you take care of the inductive kickback, you might be able to use a MOC3xxx series device directly. Normally they fire triacs. They will run <30mA at 220Vac into a small load if that's what you need. Read the data sheets carefully, there are some gotchas when used like this. For 5V several optoisolators will work. Look for a darlington type, it will be more appropriate for a TTL level switch. Maybe take a DVM set it on current scale and plug it in parallel with the switch. This will tell you the current you really need to switch. I bet about 400 uA to 1 mA for a LS TTL input with some internal pullup. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Vasile Surducan wrote: {Quote hidden}> > On Fri, 3 Aug 2001, Roman Black wrote: > > > Have you considered a relay? A "real" relay that > > is! :o) Simple to drive with your PIC and should > > work your AC fan load ok since you say it is low > > power. > > -Roman > > Roman, Nick, what do you say about this: > > One npn transistor driven in base through a resistence from pic, > transistor will short circuit ( when is on ) the +/- section of one > rectifying bridge, colector to +bridge pin, emiter to -bridge pin and > GND of pic supply. In series with ~ bridge pin, the fan , the other fan > pin and ~ pin of the bridge to AC. > ( same configuration like those used for driving full AC load using > thyristors but with transistors ) > I think will work ok and will be better than a relay. > Vasile Yep that would work for the AC load, someone mentioned that old tape decks used that system for speed control. BUT it doesn't give safe isolation. :o) -roman -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> if the load is > inductive (or capacitive) there will be a phase shift between the DC > voltage and DC current. However, the fact remains that a triac will turn > off when conducting the DC current of a half or full wave rectified signal. It's more than just a phase shift issue. Series inductance can cause the current to never reach zero (or fall below the triac dropout current). ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, TakeThisOuTolin.....TakeThisOuTembedinc.com, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservKILLspamspammitvma.mit.edu with SET PICList DIGEST in the body

At 08:33 AM 8/3/01 -0400, you wrote: >> if the load is >> inductive (or capacitive) there will be a phase shift between the DC >> voltage and DC current. However, the fact remains that a triac will turn >> off when conducting the DC current of a half or full wave rectified >signal. > >It's more than just a phase shift issue. Series inductance can cause the >current to never reach zero (or fall below the triac dropout current). Well, it obviously *must* pass through zero twice per cycle. But the problem with inductive loads is that excessive dv/dt during the time period when the current is less than the holding current (passing through zero), particularly for triacs, may prevent commutation from reliably occuring. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffRemoveMEinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

> I think everyone is missing my point... I was hesistant to say I was > connecting +5 to Gnd because then I would get the "use a transistor" > message. And a real relay is great, but I don't like the extra hardware > involved, I'm looking for something simple, all I'm doing is shorting > leads! So I guess you are saying the most important concearn is that this be a single part solution? If that is truly the case, try a logic level FET. However, if you are switching something with coils, like a fan, then you still need a flyback diode backwards accross the load. This is true no matter what method you use to switch. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, olinEraseMEembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu

> >> if the load is > >> inductive (or capacitive) there will be a phase shift between the DC > >> voltage and DC current. However, the fact remains that a triac will turn > >> off when conducting the DC current of a half or full wave rectified > >signal. > > > >It's more than just a phase shift issue. Series inductance can cause the > >current to never reach zero (or fall below the triac dropout current). > > Well, it obviously *must* pass through zero twice per cycle. A full wave rectified sine wave with no DC is ABS(SINE()). This goes to zero twice per cycle for a short time (instantaneously with perfect rectifiers). Now imaging this signal connected to a sufficiently large inductor and some resistance. Since this signal has an average DC component, there will be an average DC current thru the inductor, which will be AVE(ABS(SINE()))/R. The current in the inductor will lag the rectified voltage, but will also "average" it. With an inductance of 0 the current will be ABS(SINE())/R. With an infinite inductor in steady state, the current will totally flat at AVE(ABS(SINE)))/R. Real inductances will vary it between these two extremes, but lowest point in the current waveform will rise from 0 when the inductance is increased from 0. For real world parts some minimum inductance will be required to overcome the finite time the voltage is 0 due to voltage drops in the rectifiers and to get past the SCR holding current. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, @spam@olinRemoveMEEraseMEembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-request@spam@mitvma.mit.edu