Eurorack triggering Bent Drum with Reed Relays

[boneless]

Lately I've been experimenting with reed relays sequencing my circuit bent gear. Using Coto 9007-05-01 relays I've found the gate of most Eurorack modules is enough to switch them, so no extra power source is needed for this use.

A link to a crappy youtube and blog post here if you're interested!

Wondered what other things folk had done using them?

Thanks

PS Sorry I haven't been round these parts for a few years– general life stuff hasn't afforded me as much free time as i'd like (!)

[Circuitbenders]

Are you driving the relays directly?

I'm not sure thats a very good idea. Usually you'll switch a relay on and off via a transistor, with a diode in parallel with the relay as protection from the voltage spike you get every time the relay turns off.

[boneless]

oh crap– just seen your reply.

5v gate comes in from modular >>> I then have have an LED and 1K resistor going to ground, and to the Reed relay.

So I guess the LED and resistor is equivalent to diode in parralel with reed.

I'm not using a transistor though...

Advice would be appreciated!! Thanks!

[Circuitbenders]

Do a search on google images for 'relay transistor circuit' or similar.
I think your protection diode has to be the opposite polarity to the way you'd light an LED.

[boneless]

ok– thanks

you're right– the protection diode goes the opposite way.

The relay  I'm using has someting called a 'Optional Coil Suppression Diode' in it

http://www.farnell.com/datasheets/1691246.pdf Not sure what that does, but I'm hoping this means  they have protection diodes in built.

Adding protection diodes to my stripboard will be fine but transistors will require a re-think becasue I'm guessing I won't be able to run it all off the 5v gate in...?

f**KK it!!! Knew it couldn't be that simple!

[Circuitbenders]

Hmm, when it says optional diode, i suspect it means just that. They can be ordered with a diode, but normally they don;t have have one. The schematic diagram at the bottom of the datasheet would suggest they don't.

Are you aware that you can buy 2, 4, or 8 channel relay boards from ebay, that already have transistors and LED's built in? You can get ones that will easily be driven by a 5v gate. http://www.ebay.co.uk/itm/252051910091
They're proper relays, so they're going to click a bit, but you can get ones with silent solid state relays for a bit more

[boneless]

BLIMEY - no not seen these before– I'm amazed– thank you! That will save a ton of hassle– god bless these chinese factories!

They don't seem to have any diagrams though?  Further to your last post I now want my Eurorack gate IN to be completely islolated from any nasty shit >>> i.e. spikes from the switches, from my bent toys– and to be powered from a separate power battery or power supply (which is also completely isolated from my gates!) I Don't even want my gate's 0v to be connected to it. Having read up some more I've become paranoid!

And I haven't a clue about current draw...

In your opinion would a suitable solid state version be something  like this?

http://www.ebay.co.uk/itm/4-Channel-5V-SSR-Solid-State-Relay-2-Amp-Available-in-UK-Arduino-Raspberry-Pi-/141931636509?hash=item210bc8e71d:g:TtsAAOSwAYtWPxyT

Silent operation would be good as I had been miking the crap speakers on my toys for super lo-fi sound rather than using line out...

Many thanks for any advice.

(ps just seen yr modded tr77 on ebay. absolutely lovely!)

[Circuitbenders]

That should work fine. They're designed to be driven by microcontroller outputs, so a 5v gate from a modular won't be a problem. If you can use them to switch 240v, than you can pretty much guarantee that the input is completely isolated from everything that might cause any issues.

The point of using transistors is that you only need a tiny current to switch the much larger current that drives the relays.

In theory you could probably use a 4066 switch IC for this, but the relay board would probably take whatever you can throw at it without any fuss whatsoever.

[boneless]

Thanks again for the reply...

Ahh yes I have diddled with the CMOS 4066 on breadboards after reading Nicholas Collins book– but I've not a 'grounded' knowledge of currents/voltages and effects of mixing them, so was hoping for a solution that would keep things isolated and safe.

One last question please–

As you say this SSR board is designed for use with arduino so as I understand it, the DC+ and - would ususally be provided the arduino board, alongside the trigger in, if  so am I able to supply my own current to it from a separate PSU or battery, and if so what voltage and current would it require?

These chinese written specs never seem to be that explicit– it does mention 'Input Power: 5V DC (160mA)' but does that refer to the trigger in voltages, or the DC needed to run the relay switches...!!!! 

[Circuitbenders]

Well the information on that ebay listing has separate values for "Input Power: 5V DC (160ma)" and "Input control signal voltage: (0-2.5V state low relay OFF) (3.3-5V state high relay ON)".
That would suggest you need to power the board with 5v, and the switching signals can be between 3.3v and 5v for logic high, which would make sense as those are the two most common microcontroller signal voltages.

In terms of a power supply, i guess anything that can deliver 5v at around 200ma or more would do the job. I'm not sure what all that "4 road 5v, working current 48ma" is about, but i wouldn't worry about it.

If you are using a separate power supply to the supply thats running your eurorack trigger thing, make sure you link the grounds, or it may behave a little strangely.

[boneless]

Many thanks...

will post when I get it finished...



(ps sadly missed out on the tr77 - lovely bit of kit though– not surprised it went outta my budget!)

[boneless]

Hello all,

a bit more about the reed relay COTO 9007-05-01's that I used originally.

An email from COTO below clarifying what the 'Optional Coil Suppression Diode' is...

Dear Neal,

Thanks for your inquiry.
Please have a look at our datasheet 9007-05-01 page 2.
As you can see the diode cathode is connected with pin# 2  +5V and the diode anode is connected with pin# 3 GND.
After coil de-energization the coil generates a voltage spike which is discharged via the diode.
Please check the distribution stock material via:   http://dilp.netcomponents.com/coto.html

Let me know if you need further help.
Have a great day!

Best Regards / Mit freundlichen Gruessen
Ulrich Ehemann

So the suffix 01 means it has a protection diode in built. Very handy!

[kloroplaster]

How is it going with the relays boneless?

Could these relays be powered from the battery/power source of the bent toy? I want to try to trigger my bent stuff with the modular too!

[boneless]

I ended up making 8x midiwidget gates to switches using the coto's http://nealbeardahm.blogspot.co.uk/2016/04/midiwidget-syncs-bent-beats.html

Didn't get much farther re eurorack gating reeds directly

i had been usign the coto's, which do have a suppression diode in em, but still got spooked about the prospect of a spikes.

and the midiwiget has been doing the job for me...

stil thinking on it though, let me know how you get on...