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 Forum index » DIY Hardware and Software » Thomas Henry designs
ADV-MIDI Driving a Relay
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Thomas Henry



Joined: Mar 25, 2007
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PostPosted: Tue Aug 28, 2007 8:58 pm    Post subject: ADV-MIDI Driving a Relay Reply with quote  Mark this post and the followings unread

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
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Randaleem



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PostPosted: Wed Aug 29, 2007 5:11 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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State Machine
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PostPosted: Sat Sep 01, 2007 2:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
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?


Five millisecond switching and a SPDT arrangement, sounds like a good application for an analog switch if the current requirements are not demanding and it really doesn't seem the case according to what you are saying. You are just emulating some switch contacts on a foot pedal. You can also take a CD4066/MC14066 and a single transistor inverter to drive two switches out of phase and make a SPDT out of that and probably get job done. Also no "snubber" diodes to eliminate any high voltage spikes used with conventional relays.

Let me know ......... Very Happy I have a bunch of DGxxx series switches hanging around also. I also have some Maxim analog switch IC's hanging around also. Very Happy I am sure we can get something working Very Happy

Oh, I have a package in the mail for you so keep an eye out for it Wink

Bill
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Thomas Henry



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PostPosted: Sun Sep 02, 2007 9:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

State Machine wrote:

Five millisecond switching and a SPDT arrangement, sounds like a good application for an analog switch if the current requirements are not demanding and it really doesn't seem the case according to what you are saying. You are just emulating some switch contacts on a foot pedal. You


Yes, the 4016 occurred to me early on. But here's the deal, I'm controlling a unit whose input I know nothing about. I haven't the faintest what sort of electrical standards the footswitch input obeys, and given that it costs $350 don't want to take the risk of blowing it. A relay is totally innocuous here, but a CMOS switch...well, it probably is, too, but I sure don't want to take the risk without knowing more. Moreover, interfacing CMOS to external jacks is always a bit problematic (static, etc.). Call me a nervous nellie, but CMOS makes me wet my pants in this sort of application.

State Machine wrote:

can also take a CD4066/MC14066 and a single transistor inverter to drive two switches out of phase and make a SPDT out of that and probably get job done.


Actually, since the 4016/4066 is a quad package, a person could make a SPDT with no extra transistor needed.

State Machine wrote:

Oh, I have a package in the mail for you so keep an eye out for it Wink


Good deal; I'll look forward to it!

Thanks,

Thomas Henry
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State Machine
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PostPosted: Sun Sep 02, 2007 10:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

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



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PostPosted: Sun Sep 02, 2007 11:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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State Machine
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PostPosted: Mon Sep 03, 2007 9:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
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!)


Bingo ........ now I see. NICE ... Very Happy Very Happy Very Happy Had to sink in there. Hmm, let me draw that one ........

Thanks !
Bill


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EdisonRex
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PostPosted: Mon Sep 03, 2007 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

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.

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Tim Servo



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PostPosted: Mon Sep 03, 2007 2:13 pm    Post subject: ADV-MIDI Driving a Relay
Subject description: Slightly OT: educational sites
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EdisonRex wrote:
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.


Hey eRex,

If you're looking for more self-teaching info for your son, don't forget to check:

Play Hookey - good basic info on op amps, logic and more.
http://www.play-hookey.com/

Ray Wilson's primer on "Mickey Mouse" logic. Great info on implementing logic functions with a few discrete components. VERY handy.
http://www.musicfromouterspace.com/analogsynth/mmlogic.html


Tim (still learning) Servo
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EdisonRex
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PostPosted: Mon Sep 03, 2007 2:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

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

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State Machine
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PostPosted: Mon Sep 03, 2007 4:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
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.


Very good, your a good father I am sure! My mom, although was not trained in electronics. knew enough to fuel my interest in electrical things and purchased those electronics experimenters kits when I was a young age. They kept me busy for days on end! Thanks mom !!!! Very Happy Very Happy Very Happy


Bill
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EdisonRex
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PostPosted: Tue Sep 04, 2007 5:01 am    Post subject: Reply with quote  Mark this post and the followings unread

State Machine wrote:
Quote:
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.


Very good, your a good father I am sure! My mom, although was not trained in electronics. knew enough to fuel my interest in electrical things and purchased those electronics experimenters kits when I was a young age. They kept me busy for days on end! Thanks mom !!!! Very Happy Very Happy Very Happy


Bill


Funny thing, back long ago I had a Lectron set (like 1967 or 1968)... I loved that thing, had a lot of blocks for it. It taught me a lot. I was poking around for a link to show people and stumbled across them! I guess they've been around all along, just not in the states. I'm thrilled.

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Blue Hell
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PostPosted: Tue Sep 04, 2007 10:56 am    Post subject: Reply with quote  Mark this post and the followings unread

EdisonRex wrote:
stumbled across them!


Hey cool, my brother had those (I had some of the Phillips stuff myself) but I'm pretty sure it was made by Braun in those days.

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Adam-V



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PostPosted: Tue Sep 04, 2007 3:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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State Machine
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PostPosted: Tue Sep 04, 2007 4:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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State Machine
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PostPosted: Tue Sep 04, 2007 4:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Ray Wilson's primer on "Mickey Mouse" logic.


Thanks for that link Tim Very Happy Great stuff and in a pinch and very valid way to do things .... There are so many ways to do things in electronics and I get so annoyed when folks bowl you over with their opinions of how things should be done. Who says anyway ?? If the circuit works, use it man ! Lets all drink to Mickey !!! beer

Bill
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