ADV-MIDI Driving a Relay

Thomas Henry · Posted: Tue Aug 28, 2007 8:58 pm Post subject: ADV-MIDI Driving a Relay

Hello All,

I need to drive a relay from the ADV-MIDI circuit of yore. The output of the latter is the typical 2N3904 arrangement running on a +5V supply, providing a 5 mS pulse. The relay will control the footswitch input of a digital recorder (for punch-in).

Anyway, I don't know a thing about relays. (If you didn't know, I've never had a course in electronics, hence the sketchy background). I was thinking of getting a +5V relay from All Electronics for this application. Can anyone suggest what I ought to be looking for? I have no idea what parameters are important. Also, I seem to recall from some distant reading that I need to install a reversed diode to clamp negative excursions caused by reversed EMF (to keep from frying the ADV-MIDI transistor). Is that right?

I do have a ton of the ADV-MIDI PCB's and also the MTS-100 PCB's should anyone want to swap me for a relay that'll work here. I need a +5V unit, with a SPDT arrangement.

And maybe I should ask, can I expect an ON/OFF time of 5 mS or so, or is that unreasonable?

Thomas Henry

Randaleem · Joined: May 17, 2007 Posts: 456 Location: Northern CA, USA

Hi Thomas,

I have several pcb mount relays that will work in your application. What is your contact Volts/Amps requirement?

This, plus coil voltage and resistance constitute a full spec.

I have both a 14Pin dip package (same footprint, but thicker by about 1/8"), and a std size (.800 x .625 x .800 tall.) PCB relay with 10A contacts. Both are 5v coil, SPDT, sitting in front of me and could be on their way to you later today if you can use them. If you need more than one I have at least a dozen of each type.

You are correct about the use of an inductive spike clamping diode. A 1n914 or 1n4148 will work fine at low amperage; I like to use an MRF851 at higher amperages. Or an RC snubber. (Depending upon your contact rating and current, a snubber there also can be a good idea to protect the contacts.)

One gotcha some people miss is that the DC rating for a given relay's contact are as you'd expect QUITE a bit lower than the AC rating. if you're switching a DC load, be sure to check this particular spec carefully.

5ms is a reasonable switching time. Should be no problems there with most any garden variety PCB mount relay.

Kind regards,

Randal

State Machine · Posted: Sat Sep 01, 2007 2:53 pm Post subject:

Thomas Henry · Posted: Sun Sep 02, 2007 9:57 pm Post subject:

State Machine · Posted: Sun Sep 02, 2007 10:27 pm Post subject:

Yes, I would be cautious to Very Happy

Oh, I have attached a diagram I just put together that shows what I meant about using a 4066 as a SPDT switch ...

Bill

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Thomas Henry · Posted: Sun Sep 02, 2007 11:10 pm Post subject:

Again, the transistor is superfluous. Just use one of the other switches as an inverter instead of the transistor. That's a trick I pulled some 25 years ago with the ADSR or PAL filter (it's so long ago, I can't even recall which!)

Along these lines, did anyone notice my 4016 as an XOR trick which does something similar?

Thomas Henry

State Machine · Posted: Mon Sep 03, 2007 9:31 am Post subject:

EdisonRex · Posted: Mon Sep 03, 2007 1:58 pm Post subject:

wow, that's about as simple as it gets.

I think I'm going to use that as instruction for my younger son's electronics course (he is home schooled) this term, after we have done some TTL and CMOS logic equivalents.

Thank you for that. These gems come out of nowhere.

Tim Servo

EdisonRex · Posted: Mon Sep 03, 2007 2:35 pm Post subject:

Tim, I am reading Ray's site for ideas, but that second site you cited, is quite a sight. You guys are great helpers. He is so psyched to "melt metal", and he's been making his own circuits with the blocks, I bought some stripboard to train him on soldering (he can use my rosin core lead solder, and i'll pretend RoHS doesn't exist) and we're going to breadboard on the protoboard and then transfer to stripboard.

I think I want him to build a Soundlab for himself. I was thinking I wanted him to build me some modules, but that'd be for me, not for him. I think a Soundlab would do him good. That said, knowing him, he'll want more. Good thing I have a resource!

I'll definitely use that website, thanks so much for the link. Very Happy

State Machine · Posted: Mon Sep 03, 2007 4:37 pm Post subject:

EdisonRex · Posted: Tue Sep 04, 2007 5:01 am Post subject:

blue hell · Posted: Tue Sep 04, 2007 10:56 am Post subject:

Adam-V · Posted: Tue Sep 04, 2007 3:45 pm Post subject:

That's awesome! I had one of the Philips sets when I was a kid (kit 2040 actually). It was probably the only one in existence in Australia at the time. The manual was in Dutch, I didn't understand a word of it but it didn't stop me building the circuits and having a lot of fun with it.

Cheers,
Adam-V

State Machine · Posted: Tue Sep 04, 2007 4:02 pm Post subject:

Wow, Lectron ......... Electronic Lego Blocks !!!

Oh crap, I would have had fun with those !!! Thanks for the link. I have never seen those before !

Bill

State Machine · Posted: Tue Sep 04, 2007 4:09 pm Post subject: