Post by thread:[EE:] Detecting a blown lamp

Hi Everyone, I'm making a little PIC-controlled floodlight interface for my house, and I'd like the PIC to be able to detect if the lamp filament is working. The PIC is running off a 7805 from a wall-adapter, and is happily controlling the floodlight via a triac. The floodlight is running off a 240vAC fused spur and is rated for 500W. I have another floodlight I'd like to use for a second interface that is 250W, so I'd like to be able to create a 'generic' broken-filament detector that doesn't rely on there being a specific wattage of bulb. I've seen the X-10 Microchip app note where they just use a mega Ohm resistor to connect a PIC pin up to the mains for the zero-crossing detect, but I'm not sure on the safety issues of that one. My other idea was a transistor with it's base connected via a suitably sized resistor to the 240v live just before the floodlight. The transistor would drive an optoisolator. I've seen something similar on piclist.com describing a stalled motor detector, but I've no idea if it would work with a lamp of variable wattage at 240vAC. Any thoughts/ideas appreciated. Cheers, Tim

Tim ODriscoll wrote: > The PIC is running off a 7805 from a wall-adapter, and is happily > controlling the floodlight via a triac. The floodlight is running off a > 240vAC fused spur and is rated for 500W. I have another floodlight I'd > like to use for a second interface that is 250W, so I'd like to be able > to create a 'generic' broken-filament detector that doesn't rely on > there being a specific wattage of bulb. > > I've seen the X-10 Microchip app note where they just use a mega Ohm > resistor to connect a PIC pin up to the mains for the zero-crossing > detect, but I'm not sure on the safety issues of that one. The the pic is totally isolated from everything but A/C, that would work. There are tricks they are doing there that, if you tie the pic to (say) a RS-232 port on a PC, will probably cause sparks and/or smoke at the least. > My other idea was a transistor with it's base connected via a suitably > sized resistor to the 240v live just before the floodlight. The > transistor would drive an optoisolator. I've seen something similar on > piclist.com describing a stalled motor detector, but I've no idea if it > would work with a lamp of variable wattage at 240vAC. You need to detect current flow, not just voltage, right? How about a very small resistance between the triac's output and the lamp, and measure the voltage drop across it somehow? Opto-isolate that and you'll make it safe. --Michael

hi, the method i've used previously is the current loop/transformer method. You only need around 25mA for driving a burden resistor which can then be monitored by a pic a/d port. The trafo will be quite small, in the region of say 1cm^2 This also makes it electrically isolated. On 12/14/05, M Graff <spam_OUTexplorer-piclistTakeThisOuTflame.org> wrote: {Quote hidden}> > Tim ODriscoll wrote: > > The PIC is running off a 7805 from a wall-adapter, and is happily > > controlling the floodlight via a triac. The floodlight is running off a > > 240vAC fused spur and is rated for 500W. I have another floodlight I'd > > like to use for a second interface that is 250W, so I'd like to be able > > to create a 'generic' broken-filament detector that doesn't rely on > > there being a specific wattage of bulb. > > > > I've seen the X-10 Microchip app note where they just use a mega Ohm > > resistor to connect a PIC pin up to the mains for the zero-crossing > > detect, but I'm not sure on the safety issues of that one. > > The the pic is totally isolated from everything but A/C, that would > work. There are tricks they are doing there that, if you tie the pic to > (say) a RS-232 port on a PC, will probably cause sparks and/or smoke at > the least. > > > My other idea was a transistor with it's base connected via a suitably > > sized resistor to the 240v live just before the floodlight. The > > transistor would drive an optoisolator. I've seen something similar on > > piclist.com describing a stalled motor detector, but I've no idea if it > > would work with a lamp of variable wattage at 240vAC. > > You need to detect current flow, not just voltage, right? > > How about a very small resistance between the triac's output and the > lamp, and measure the voltage drop across it somehow? Opto-isolate that > and you'll make it safe. > > --Michael >

On Wed, 2005-12-14 at 10:11 -0600, M Graff wrote: > Tim ODriscoll wrote: > > The PIC is running off a 7805 from a wall-adapter, and is happily > > controlling the floodlight via a triac. The floodlight is running off a > > 240vAC fused spur and is rated for 500W. I have another floodlight I'd > > like to use for a second interface that is 250W, so I'd like to be able > > to create a 'generic' broken-filament detector that doesn't rely on > > there being a specific wattage of bulb. > > > > I've seen the X-10 Microchip app note where they just use a mega Ohm > > resistor to connect a PIC pin up to the mains for the zero-crossing > > detect, but I'm not sure on the safety issues of that one. > > The the pic is totally isolated from everything but A/C, that would > work. There are tricks they are doing there that, if you tie the pic to > (say) a RS-232 port on a PC, will probably cause sparks and/or smoke at > the least. Trouble is that my floodlight interface is on an rs485 bus, part of which is an rs232 interface to a PC so I can log everything :-) > You need to detect current flow, not just voltage, right? Yes. > How about a very small resistance between the triac's output and the > lamp, and measure the voltage drop across it somehow? Opto-isolate that > and you'll make it safe. I've seen 'current-sense' resistors, which are in the milli-Ohms.. They're only rated for a few watts though.. I'm guessing that I need one which is rated for the same as the floodlight, right? But that's 500W.. Or maybe I'm a little rusty on all that :-) Cheers, Tim

On Wed, 2005-12-14 at 19:46 +0200, John Ward wrote: > hi, the method i've used previously is the current loop/transformer method. OK, I admit that I've never heard of that and I don't quite understand it.. Google isn't helping me much on it either.. Can you elaborate? > You only need around 25mA for driving a burden resistor which can then be > monitored by a pic a/d port. Have you seen this method documented anywhere on the Internet? It sounds interesting and I'd like to know more.. > The trafo will be quite small, in the region of say 1cm^2 Small is good... > This also makes it electrically isolated. Excellent. Cheers, Tim

Tim, you can do that when the light is off by connecting 10 meg resistor + diode after your light bulb where it gets connected to triac to one of pic pin. make sure your light bulb is connected to HOT wire software function: 1. turn off the light thru pic 2. check thru resistor logic 1 ? 3. if it is 1 then the bulb is there 0 means open 4. if 1 turn the light on 5. check thru resistor again if 0 it means it is working if 1 your triac is open now you can check if your traic is working too Andre Abelian Tim ODriscoll wrote: {Quote hidden}>Hi Everyone, > >I'm making a little PIC-controlled floodlight interface for my house, >and I'd like the PIC to be able to detect if the lamp filament is >working. > >The PIC is running off a 7805 from a wall-adapter, and is happily >controlling the floodlight via a triac. The floodlight is running off a >240vAC fused spur and is rated for 500W. I have another floodlight I'd >like to use for a second interface that is 250W, so I'd like to be able >to create a 'generic' broken-filament detector that doesn't rely on >there being a specific wattage of bulb. > >I've seen the X-10 Microchip app note where they just use a mega Ohm >resistor to connect a PIC pin up to the mains for the zero-crossing >detect, but I'm not sure on the safety issues of that one. > >My other idea was a transistor with it's base connected via a suitably >sized resistor to the 240v live just before the floodlight. The >transistor would drive an optoisolator. I've seen something similar on >piclist.com describing a stalled motor detector, but I've no idea if it >would work with a lamp of variable wattage at 240vAC. > >Any thoughts/ideas appreciated. > >Cheers, > >Tim > > >

Any reason not to simply look for the light when the lamp is on? You know using an opto detector of some type. Larry {Quote hidden}> > From: Tim ODriscoll <.....timKILLspam@spam@stokepogesway.net> > Date: 2005/12/14 Wed PM 02:48:39 EST > To: "Microcontroller discussion list - Public." <piclistKILLspammit.edu> > Subject: Re: [EE:] Detecting a blown lamp > > On Wed, 2005-12-14 at 19:46 +0200, John Ward wrote: > > hi, the method i've used previously is the current loop/transformer method. > > OK, I admit that I've never heard of that and I don't quite understand > it.. Google isn't helping me much on it either.. Can you elaborate? > > > > You only need around 25mA for driving a burden resistor which can then be > > monitored by a pic a/d port. > > Have you seen this method documented anywhere on the Internet? It sounds > interesting and I'd like to know more.. > > > > The trafo will be quite small, in the region of say 1cm^2 > > Small is good... > > > > This also makes it electrically isolated. > > Excellent. > > Cheers, > > Tim > > --

On 15/12/05, Jinx <EraseMEjoecolquittspam_OUTTakeThisOuTclear.net.nz> wrote: > > transistor would drive an optoisolator > > I vaguely recall a "blown-fuse indicator" which has an LED + > resistor across the filament. When the filament is OK, next to > nothing will flow through the LED + R (the filament being so > much lower resistance than R). If the filament blows, the LED > will light > > -- Sorry, I can't see this working. The standard circuit has very low source impedance so the voltage accross the bulb will be the same whether it's good or bad. The situation is different in a fusefail detector as normally there is a load in series as well and its impedance should be much higher than that of the fuse. You either need to measure the current when you know it's turned on, or use an optical setector to figure out if its bright. RP

Tim, Assuming you have some form of PCB to mount the triac on, make the output trace nice and wide and straight. Tthen cut two slots each side parallel with this output trace. Then wrap some very small thin, insulated wire perpendicular to the trace and using the two slots keep wrapping so you circle the output trace. This wound wire will pick mains hum and create a current from it, etc etc Then feed this into an op amp, convert the ac to dc (possibly before the op amp) and you'll have a pcb mounted current sensor. If the light is on current flows, if not none flows... Nice and simple and isolated from the mains. I've never tried this but I did think the idea up a while ago when I was stuck in traffic and wondered how my car's ECU knows when a bulb has blown. I'm also no expert on mains and current and such stuff, so it might not work at all but I thought it was an idea that might be worth sharing... Good luck... Cheers Kev/. {Original Message removed}

On 15/12/05, Kev Pearce (kevp.com) <listsspam_OUTkevp.com> wrote: {Quote hidden}> Tim, > > Assuming you have some form of PCB to mount the triac on, make the output > trace nice and wide and straight. Tthen cut two slots each side parallel > with this output trace. Then wrap some very small thin, insulated wire > perpendicular to the trace and using the two slots keep wrapping so you > circle the output trace. This wound wire will pick mains hum and create a > current from it, etc etc > > Then feed this into an op amp, convert the ac to dc (possibly before the op > amp) and you'll have a pcb mounted current sensor. > > If the light is on current flows, if not none flows... > > Nice and simple and isolated from the mains. > > I've never tried this but I did think the idea up a while ago when I was > stuck in traffic and wondered how my car's ECU knows when a bulb has blown. > I'm also no expert on mains and current and such stuff, so it might not work > at all but I thought it was an idea that might be worth sharing... > > Good luck... > > > Cheers > > Kev/. > > > {Original Message removed}

part 0 44 bytes his is a multi-part message in MIME format. part 1 1302 bytes content-type:text/plain; charset=ISO-8859-1; format=flowed (decoded 7bit) Tim ODriscoll wrote: >Hi Everyone, > >I'm making a little PIC-controlled floodlight interface for my house, >and I'd like the PIC to be able to detect if the lamp filament is > > >My other idea was a transistor with it's base connected via a suitably >sized resistor to the 240v live just before the floodlight. The >transistor would drive an optoisolator. I've seen something similar on >piclist.com describing a stalled motor detector, but I've no idea if it >would work with a lamp of variable wattage at 240vAC. > >Any thoughts/ideas appreciated. > >Cheers, > >Tim > > > My memory is sketchy on this but I remember as a kid 50 some years ago. We took a neon bulb and soldered 2 pieces of bell wire. ( about 18 or 20 ga.solid copper wire with low voltage insulationused on battery door bell circuit. we would take one lead and ground it and the other lead we would wrap around the hot lead going to the powered device. (bulb in this case)When current would flow through the wire the neon light would light no current the neon was off. I cannot remeber if we added resistors or not. All you would have to dois detect the neon light on or off. maybe watch the plasement of the coil too. part 2 391 bytes content-type:text/x-vcard; charset=utf-8; (decoded 7bit) begin:vcard fn:Robert I. Nelson n:Nelson;Robert I. org:RIN Designs adr:;;P.O. BOX 373;RIPON;WI;54971;USA email;internet:KILLspamrindesignsKILLspamcharter.net tel;work:1-(920)-229-7152 tel;home:1-(920)-748-7443 note;quoted-printable:Custom design and building of small electro mechanical devices.=0D=0A= AUTOCAD work ver2002 x-mozilla-html:FALSE version:2.1 end:vcard part 3 35 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)

Perhaps HEAT could be detected? R. I. Nelson wrote: {Quote hidden}> Tim ODriscoll wrote: > >> Hi Everyone, >> >> I'm making a little PIC-controlled floodlight interface for my house, >> and I'd like the PIC to be able to detect if the lamp filament is >> >> >> My other idea was a transistor with it's base connected via a suitably >> sized resistor to the 240v live just before the floodlight. The >> transistor would drive an optoisolator. I've seen something similar on >> piclist.com describing a stalled motor detector, but I've no idea if it >> would work with a lamp of variable wattage at 240vAC. >> >> Any thoughts/ideas appreciated. >> >> Cheers, >> >> Tim >> >> >> > My memory is sketchy on this but I remember as a kid 50 some years > ago. We took a neon bulb and soldered 2 pieces of bell wire. ( about > 18 or 20 ga.solid copper wire with low voltage insulationused on > battery door bell circuit. we would take one lead and ground it and > the other lead we would wrap around the hot lead going to the powered > device. (bulb in this case)When current would flow through the wire > the neon light would light no current the neon was off. I cannot > remeber if we added resistors or not. > > All you would have to dois detect the neon light on or off. maybe > watch the plasement of the coil too. >

> > > My memory is sketchy on this but I remember as a kid 50 some years ago. > We took a neon bulb and soldered 2 pieces of bell wire. ( about 18 or 20 > ga.solid copper wire with low voltage insulationused on battery door > bell circuit. we would take one lead and ground it and the other lead > we would wrap around the hot lead going to the powered device. (bulb in > this case)When current would flow through the wire the neon light would > light no current the neon was off. I cannot remeber if we added > resistors or not. > > All you would have to dois detect the neon light on or off. maybe watch > the plasement of the coil too. > I've used a similar method to this also - but it detects (AC) voltage on the wire - not current passing through it. It could be used in this situation to detect if the light is turned on - then the result "anded" with the current sensor to check that current is flowing. RP

On Wed, Dec 14, 2005 at 07:43:00PM +0000, Tim ODriscoll wrote: > I've seen 'current-sense' resistors, which are in the milli-Ohms.. > They're only rated for a few watts though.. I'm guessing that I need one > which is rated for the same as the floodlight, right? But that's 500W.. > Or maybe I'm a little rusty on all that :-) Nope, think in terms of the power dissipating by the resistor. So for instance: 120V AC 500W Through therefore: Power = Current * Voltage 500W = I * 120V I = 4.16A So we've got 4 amps flowing through the AC line right. Now if we add in that 0.1ohm resistor we can calculate the voltage drop accross it: V=4.16A*0.1R V=0.416V Now think of it this way, the resistor is droping the voltage by converting electric power to heat. So we can calculate the amoung of heat it generates doing that using the power equation: P=IV P=4.16A*0.416V P=1.731W More than your average quarter watt resistor for sure, but a 10W resistor is totally fine for that purpose. -- RemoveMEpeteTakeThisOuTpetertodd.ca http://www.petertodd.ca

part 1 440 bytes content-type:text/plain; (decoded 7bit) > a blown fuse indicator that used an LED, maybe I should > track the ciruit down to see exactly how it was done I think I found the one I was thinking of. It appears to be suitable only for DC though (in its present form anyway). A couple of others I found are also for loaded DC Another suggestion was this simple field detector. A piece of wire acting as an antenna is wound around the cable part 2 1877 bytes content-type:image/gif; (decode) part 3 1045 bytes content-type:image/gif; (decode) part 4 35 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)

Remember this ? ----- Original Message ----- From: "Marcel Birthelmer" <spamBeGonemarcelspamBeGonecarrietech.com> To: "Microcontroller discussion list - Public." <TakeThisOuTpiclistEraseMEspam_OUTmit.edu> Sent: Sunday, August 21, 2005 1:08 PM Subject: [EE]: appliance current sensor Hello all; random project time. This is the situation: of the three people I'm sharing a house with, I'm the only one whose room is not adjoined to the garage. This means that I can never hear when the washer or dryer are done, and so my laundry scheduling is always suboptimal. Now of course I could just set my watch or whatever, but where's the fun in that. One additional criterium that will come in is that these are not my appliances, so I can't open them. Now, I was thinking that it should be possible to pick up the current draw of those appliances and then, via a small embedded system or maybe an old computer, forward this information to the local network or something ----- Original Message ----- From: "Jinx" <RemoveMEjoecolquittTakeThisOuTclear.net.nz> To: "Microcontroller discussion list - Public." <piclistEraseME.....mit.edu> Sent: Sunday, August 21, 2005 3:25 PM Subject: Re: [EE] appliance current sensor {Quote hidden}> > If a high-permeability core goes around both conductors, then > > the fields cancel out pretty well > I just tried a UGN3503 on our washing machine lead and had > no problem picking up a distinctive 30mV 50Hz signal when the > sensor is over the active and the machine is turned on. There is > negligible signal when the machine is turned off. Enough of a > difference to detect, even unamplified, with a PIC comparator > or ADC

Hi Everyone, I've found a toroidal current sense pcb-mounted device for a little over one UK pound. Excellent. It says it's suitable for 50Hz AC voltage and 1A to 10A. It's basically a rectangle with a hole in the middle for the current-carrying cable, and two pins underneath it for the output. The datasheet states that there is 50 ohms resistance between the two pins and the graph implies that I should see 4mV to 5mV for 1A and 7.5mv for 2A. That means I should be able to detect what kind of bulb is in the light too, right? Cool. The two possible bulbs are 250W and 500W, and I live in the UK, so it's 230vAC. I've never used the A/D port on a pic before, but I've got a 16f628 earmarked for this, which has one I believe. How does one connect up this current-sensing coil to a pic a/d pin then? I'm assuming something nice and simple like I ground one end of the coil and just wire the other directly into the a/d port, then it's all software? Or would that not yield any input? Cheers, Tim.

On Wed, 14 Dec 2005, John Ward wrote: > hi, the method i've used previously is the current loop/transformer method. > > You only need around 25mA for driving a burden resistor which can then be > monitored by a pic a/d port. > The trafo will be quite small, in the region of say 1cm^2 If you do not need to sense the failed lamp *immediately* then a thermistor wired to an a/d input works fine. Could be replaced with a silicon device (e.g. NPN transistor) near the switching element. This assumes that the switching element raises by about 10 deg.C in operation. It is also possible to use a single current metering device for the entire unit (several loads) as long as the cpu can keep track of which load is on/off at any one time. Then there is a the simple load sensing device that consists of an optocoupler shunted by a few (two) silicon diodes in series with the load. Peter

> >> Any reason not to simply look for the light when the lamp > is on? You > >> know using an opto detector of some type. Larry > > > > ambient light > > But why would you be turning on a lamp if there is lots of > ambient light? And I suppose you could put an LDR near to the lamp, where the light level from the lamp would be way above the ambient light level. Or you could detect the difference between lamp off and lamp on. Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products docent Hogeschool van Utrecht: http://www.voti.nl/hvu

part 1 1126 bytes content-type:text/plain (decoded 7bit) Thanks for all the ideas.. I'd like to use the torroidal current sensor, I think.. No huge reason except that I've not tried any a/d before and I quite like the idea of being able to detect what kind of bulb is in the lamp. Although if I can't get it to work, the bridge-rectifier/opto idea would be next. I think I may have interpreted the data sheet wrong for the torroid I intend to use, so I've drawn a copy for others' opinions who have hopefully used something similar. I had inferred from the attached diagram that there was a resistance of 50 ohms through the actual device, but in retrospect, I think it may mean I have to supply one externally. I'm still not having any luck with Google in finding out how to hook up one of these things either.. I used to like those 'example circuits' and 'typical applications' at the end of data sheets.. It's probably one of those things that's so simple everyone already knows so no-one thinks of writing it down.. Now I know how my Mum feels when she tries something I find simple like setting the clock on the microwave.. Cheers, Tim. part 2 1745 bytes content-type:image/gif; name=toroidal.gif (decode) part 3 35 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)

{Quote hidden}>-----Original Message----- >From: RemoveMEpiclist-bouncesEraseMEEraseMEmit.edu [RemoveMEpiclist-bouncesspam_OUTKILLspammit.edu] >Sent: 15 December 2005 22:58 >To: Microcontroller discussion list - Public. >Subject: Re: [EE:] Detecting a blown lamp > > >Thanks for all the ideas.. > >I'd like to use the torroidal current sensor, I think.. No >huge reason except that I've not tried any a/d before and I >quite like the idea of being able to detect what kind of bulb >is in the lamp. Although if I can't get it to work, the >bridge-rectifier/opto idea would be next. > >I think I may have interpreted the data sheet wrong for the >torroid I intend to use, so I've drawn a copy for others' >opinions who have hopefully used something similar. I had >inferred from the attached diagram that there was a resistance >of 50 ohms through the actual device, but in retrospect, I >think it may mean I have to supply one externally. > >I'm still not having any luck with Google in finding out how >to hook up one of these things either.. I used to like those >'example circuits' and 'typical applications' at the end of >data sheets.. It's probably one of those things that's so >simple everyone already knows so no-one thinks of writing it >down.. Now I know how my Mum feels when she tries something I >find simple like setting the clock on the microwave.. > >Cheers, > >Tim. > Tim, Essentialy this device is a transformer, only output voltage is proportional to the current in the primary, as opossed to the voltage accross the primary of a conventional transformer. The output is an AC signal, most definately NOT suitable for feeding directly into the PIC's AD port. You will need some signal conditioning first, namely rectification and amplification (and possibly some filtering). A link to the datasheet for the device would be helpfull. If the output really is as small as you say (i.e. a few mV) you will have to use a precision rectifier circuit, as a normal diode would never reach conduction as such low voltages. This would need to be followed by some gain to get the voltage up to a level suitable for the PIC. If you could find a device with a higher output voltage at the current range you are using, the interface circuit design could be simplified somewhat. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =======================================================================

Mike, On Fri, 2005-12-16 at 09:42 +0000, Michael Rigby-Jones wrote: > Essentialy this device is a transformer, only output voltage is > proportional to the current in the primary, as opossed to the voltage > accross the primary of a conventional transformer. The output is an > AC signal, most definately NOT suitable for feeding directly into the > PIC's AD port. You will need some signal conditioning first, namely > rectification and amplification (and possibly some filtering). After Bob's reponse I did some more Googling and found Ed Cheung's Home Automation site where he describes using current transformers and how to build them. There's also a link on his site to a Google query 'burden resistor' which throws up a lot more useful info. I've had a jolly good read up and had surmised exactly what you mention above :-) > A link to the datasheet for the device would be helpfull. If the > output really is as small as you say (i.e. a few mV) you will have to > use a precision rectifier circuit, as a normal diode would never reach > conduction as such low voltages. This would need to be followed by > some gain to get the voltage up to a level suitable for the PIC. If > you could find a device with a higher output voltage at the current > range you are using, the interface circuit design could be simplified > somewhat. The datasheet: http://www.stokepogesway.net/~tim/datasheets/current_transformer.pdf I'm starting to think that this is getting a bit overkill, seeing as Peter's bridge-rectifier/opto seems neater.. Then again, it shouldn't cost too much more for an opamp so maybe it'll be quite interesting... Cheers, Tim.

On Fri, 16 Dec 2005, Alan B. Pearce wrote: >> I'm starting to think that this is getting a >> bit overkill, seeing as Peter's bridge-rectifier/ >> opto seems neater.. > > I know that this arrangement is used to detect the presence of a train in a > block on model railways. Yes except it works well mostly for low loads (say <1A). Beyond that it starts making a lot of heat for a small and unobtrusive circuit it is supposed to be. A Hall current sensor is not so expensive by the time you need to measure go/no go 7A and it has to take the inrush of presumably 40-50Aish gracefully (i.e. even if the filament decides to go just then). I'd still look into a simple thermistor siliconed to the insulated side of the triac with extra shrink tubing to increase insulation (you are using a triac, no?). Peter

On Fri, 2005-12-16 at 20:20 +0200, Peter wrote: > Yes except it works well mostly for low loads (say <1A). Beyond that it > starts making a lot of heat for a small and unobtrusive circuit it is > supposed to be. A Hall current sensor is not so expensive by the time > you need to measure go/no go 7A and it has to take the inrush of > presumably 40-50Aish gracefully (i.e. even if the filament decides to go > just then). I'd still look into a simple thermistor siliconed to the > insulated side of the triac with extra shrink tubing to increase > insulation (you are using a triac, no?). I am using a triac, yes. The load that the brightest lamp will cause is 2A. I have another lamp which will pull 1A. I don't know if the triac heats up much when it's on with these loads though. I have a fairly large heatsink on it, but I make a point of not touching any part of it when it's got the 240vAC going through it, so I don't know if it heats up much. Although, thinking about it, I might have a temperature probe floating around somewhere for my multimeter.. I've also got a few ds1820's too.. I'll give that a go.. Cheers Peter, Tim.

The flood light should heat up nicely. Bill ----- Original Message ----- From: "Tim ODriscoll" <RemoveMEtimTakeThisOuTspamstokepogesway.net> To: "Microcontroller discussion list - Public." <EraseMEpiclistspamspamBeGonemit.edu> Sent: Saturday, December 17, 2005 1:39 AM Subject: Re: [EE:] Detecting a blown lamp {Quote hidden}> On Fri, 2005-12-16 at 20:20 +0200, Peter wrote: >> Yes except it works well mostly for low loads (say <1A). Beyond that it >> starts making a lot of heat for a small and unobtrusive circuit it is >> supposed to be. A Hall current sensor is not so expensive by the time >> you need to measure go/no go 7A and it has to take the inrush of >> presumably 40-50Aish gracefully (i.e. even if the filament decides to go >> just then). I'd still look into a simple thermistor siliconed to the >> insulated side of the triac with extra shrink tubing to increase >> insulation (you are using a triac, no?). > > I am using a triac, yes. The load that the brightest lamp will cause is > 2A. I have another lamp which will pull 1A. I don't know if the triac > heats up much when it's on with these loads though. I have a fairly > large heatsink on it, but I make a point of not touching any part of it > when it's got the 240vAC going through it, so I don't know if it heats > up much. > > Although, thinking about it, I might have a temperature probe floating > around somewhere for my multimeter.. I've also got a few ds1820's too.. > > I'll give that a go.. > > Cheers Peter, > > Tim. > > --