Post by thread:[EE:] Analog switches

The analog switches that I have recently found, opened a new window for me. Could I use the analog switches, like MAX323, like a relay? To better explain what I am thinking, if I have circuit that works with 3V, could I use the switch to close and open a 24V line coming from outside world, thus imititating the SPST relay? Thanks in advance, Omer -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Omer, If you just want to switch high voltage ON or OFF I would use a FET ckt to do that. I would only use the analog switches if you have an analog signal that needs to be switched without loosing too much of the signal. I would check the specs closely, the current draw of whatever you're switching too and the voltage level might be too much. Steve >>> spam_OUToyalhiTakeThisOuTTEKSAN.COM.TR 4/22/2004 12:33:23 PM >>> The analog switches that I have recently found, opened a new window for me. Could I use the analog switches, like MAX323, like a relay? To better explain what I am thinking, if I have circuit that works with 3V, could I use the switch to close and open a 24V line coming from outside world, thus imititating the SPST relay? Thanks in advance, Omer -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Omer wrote... >The analog switches that I have recently found, opened a new window for me. >Could I use the analog switches, like MAX323, like a relay? To better >explain what I am thinking, if I have circuit that works with 3V, could I >use the switch to close and open a 24V line coming from outside world, thus >imititating the SPST relay? Nearly all analog switches allow switching of analog signals ONLY within the supply voltage boundaries; that is, the analog signal must be "between the rails" at all times. In the case of the MAX323, the data sheet gives a signal range of -0.3V to (V+ +0.3V) in its ABSOLUTE MAXIMUM RATINGS section, indicating that going outside this range may permanently damage the device. So, switching a 24 volt line with a MAX323 powered from 3 volts would not work. HTH... Dave D. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

You can connect N RS232 devices together in a ring topology, if the software supports it. Basically: Each message has the form of <dest><src><payload> You send your message to a recipient, and mark yourself as the source. You pass on any messages that aren't for you. You receive any messages that are for you. You swallow any messages you sent. They've gone around the ring once. You might need to do something else as the recipient is apparently asleep or gone or ? For bonus points, configure the hub so that unplugged devices are bypassed automatically (relay on CTS?) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

David VanHorn wrote: > You can connect N RS232 devices together in a ring topology, if the software supports it. > > Basically: > Each message has the form of <dest><src><payload> > > You send your message to a recipient, and mark yourself as the source. > You pass on any messages that aren't for you. > You receive any messages that are for you. > > You swallow any messages you sent. > They've gone around the ring once. You might need to do something else as the recipient is apparently asleep or gone or ? > > For bonus points, configure the hub so that unplugged devices are bypassed automatically (relay on CTS?) You're bringing back nightmares of a network that used MAU's that weren't "smart" and really really big network connectors, Dave... and it ran at 4Mb/s... Nate Duehr, .....nateKILLspam@spam@natetech.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Thursday, Apr 22, 2004, at 15:59 US/Pacific, Omer YALHI wrote: > > I have double checked the maximum ratings and you are right, I missed > that. So much for "opened windows". :-( There are small "solid-state relays" that might do the sort of thing you are looking for (but they tend to be a bit on the expensive side.) For instance, the Claire LCA110 switches up to 350V/120mA with a max Ron of 35 ohms, and comes in a 6-pin DIP. $3-4 at digikey... Found a lot in telco stuff like phone switches... BillW -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

There are a couple of factors that affect this. First, the ON resistance of most (inexpensive) analog switches is quite high (hundreds of ohms). The pricier units get that value down, but still don't want to pass a lot of current. Second, the cheaper ones (4061, 4066 etc) require control voltages in the range of the signals to be switched. Want to switch a signal that swings to +10V? You need 10V logic, and a 10V supply rail. Maxim (and others, I'm sure) make some that have dual supplies, one for analog and one for digital, but those get pricey. Your best bet is solid state relays. Jameco (for example) has some in the $2-$3 dollar range. MUCH better than most of the analog switch chips. Mike H. >The analog switches that I have recently found, opened a new window for me. >Could I use the analog switches, like MAX323, like a relay? To better >explain what I am thinking, if I have circuit that works with 3V, could I >use the switch to close and open a 24V line coming from outside world, thus >imititating the SPST relay? > >Thanks in advance, > >Omer _________________________________________________________________ Test your Travel Quotient and get the chance to win your dream trip! http://travel.msn.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

{Quote hidden}>-----Original Message----- >From: Mike Hord [gaidinmdKILLspamHOTMAIL.COM] >Sent: 23 April 2004 14:36 >To: .....PICLISTKILLspam.....MITVMA.MIT.EDU >Subject: Re: [EE:] Analog switches > > >There are a couple of factors that affect this. > >First, the ON resistance of most (inexpensive) analog switches >is quite high (hundreds of ohms). The pricier units get that >value down, but still don't want to pass a lot of current. > >Second, the cheaper ones (4061, 4066 etc) require control >voltages in the range of the signals to be switched. Want to >switch a signal that swings to >+10V? You need 10V logic, and a 10V supply rail. Maxim (and others, >+I'm >sure) make some that have dual supplies, one for analog and >one for digital, but those get pricey. > >Your best bet is solid state relays. Jameco (for example) has >some in the $2-$3 dollar range. MUCH better than most of the >analog switch chips. > >Mike H. > I thought solid state relays were Triac/SCR based and therefore only suitable for AC? Or am I way off the mark? 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. ======================================================================= Any questions about Bookham's E-Mail service should be directed to EraseMEpostmasterspam_OUTTakeThisOuTbookham.com. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Look at Jameco part numbers 172591CL, 175222CL, 176647CL, and 176655CL. Solid state relays, 3-32V DC control, switching up to 120 V DC. That said, I'm noticing that I was looking at the wrong prices and the cost is in fact somewhat higher, and I don't know exactly how they work. Mike H. >I thought solid state relays were Triac/SCR based and therefore only >suitable for AC? Or am I way off the mark? > >Regards > >Mike _________________________________________________________________ MSN Toolbar provides one-click access to Hotmail from any Web page FREE download! http://toolbar.msn.com/go/onm00200413ave/direct/01/ -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Solid State Relays come in two forms (as far as I know) - there are units using a BiPolar transistor as a switch, and others which use a FET as a switch. Both are optically coupled - a photoisolator activated by a low voltage/low current signal (5v @ 15mA) drives the switch device. The bipolar devices are intended for DC and the FET devices are often intended for AC loads. These devices are intended for switching power loads - usually 60/150 volts at anything up to several Amps. They usually include reverse voltage and spike/surge protection, so they tend to be rather expensive. Also, they are not intended for low level signal switching. This is general information - I do not know exactly what configuration the Jameco devices use. The MAXIM analog switches are just about the best units I have found for switching low-level signals - I have used them for many years in lots of different projects. Roy J. Gromlich -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

What about driving a transistor (or darlington pair) with an opto-isolator. If the transistor cost more than the opto, protect the transistor by calculating the gain so that the Opto will pop first under fault condition. Like a relay the "output switch" will be completely isolated from the switching signal. Don't forget free weeling diode when switching inductive loads. The same priciple can be used to switch ac. For ac you need to use a different Opto driving a Triac. Same principle different components. See 4N25..4n36 for DC and MOC3041 for AC Riaan {Original Message removed}

> >> I thought solid state relays were Triac/SCR based and therefore only >> suitable for AC? Or am I way off the mark? >> "power" solid state relays are usually triac based, but there are also "signal" style SSR like the LCA110 I mentioned, and they use light-activated mosfets interally (according to the clare datasheet, anyway. Don't know offhand how 'logical' vs 'real' that is.) The opto link isolates the Vgs sorts of issues, and of course you can use arbitrarilly high voltage mosfets... BillW -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.