Diy gate/trigger button circuit?

what module are you talking about ?

3 giant sized arcade buttons. It’s pretty much in all of Sam’s live performance videos, flashing to the beat. I don’t think it’s one he’s released or documented as I couldn’t see it on the website.

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Use diodes to OR the input jack and the button signal. Add a 100k pulldown after the diodes.

In that case you should not drive an LED directly with the gate signal. You’ll need to buffer it as above with a transistor, or with an op amp.

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With a gate input I’d go back to the two transistor design. Maybe something like this:

Value of R8 depends on LED and desired brightness, something like 470R or 1k maybe with typical non super bright LED.

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that looks perfect, I’ll give that a go, thanks!

It’s absolutely untested. I should update the image to clarify that.

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Hey Guy, you can replace these transistors with any other classic NPN, they will be equivalent for this application !

Have fun opening stargates and have a great trip on hyperspace !!!

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I built this the other week.

[updated schematic 2023-01-27]

A simple pulse will trigger the circuit and it will produce a gate the duration of which you can choose using the ‘LENGTH’ potentiometer. You can also use a CV signal to modulate the gate’s duration. The GATE-input is meant for gate signals the length of which you want to change.

Obviously the trigger could be from a push botton connecting the TRIGGER-input to V+.

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The power supply protection circuit will probably fail to do its job if you connect it to a power supply capable of more than 1A.
It relies on a fusible element that most power supplies don’t have on their output.
After a very short while, the diodes will blow, most likely open, and the full reverse voltage will be applied to the rest of the circuit.
If you want to go this route you should add some resettable fuses (prefered way) or use much heftier diodes (not recommended).

I understand what you mean, but the diodes are only meant for a “momentary” protection. Whenever I plug in a module during testing or for ‘production’ in my rig I keep a close eye on the power supply voltages. So I should be able to see quickly whether something goes horribly wrong, like those diodes conducting because the power lines are reversed. I’m using Behringer CP1A power supplies which have overcurrent protection. So they switch off immediately when something is wrong. As I’m using a fixed power rail and always check the flatcables I use, there is not much chance for this ever to happen. Also, with more than 10 modules per powersupply that have those diodes the total amount of current would be spread out over all of them and the power supply is likely to switch off itself because of the high current load befor any of the diodes will go up in smoke. Finally it is very unlikely for the + and - power supplies ever to change places in my rig.

Adding the diodes to the circuit is not ideal. A crow bar circuit combined with a resettable fuse would be better, but much more complicated to implement.

I understand that your design works in your particular circumstances, I guess my warning is more for people wanting to replicate your design in a more generic environment.

The diodes already essentially form the crowbar, so all that’s missing is resettable fuses. See the second part of this post for a schematic.

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There’s a whole topic of course:

I favor series Schottkys, which protect against power reversal but do not help in case of shorts and do drop a little voltage. But only a little, you shouldn’t be relying on your power rails for precise voltage values anyway, and pretty much the only time you possibly have a short is when you power up the module for the first time, and before doing that you should be testing for shorts. And series Schottkys can be easily fitted to existing PCBs in place of 10R resistors or (twitch, twitch) ferrite beads.

A matter of taste, though. Polyswitch fuses are cheap enough and if you have the PCB real estate they’re good insurance.

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Ha, I was overthinking the crow bar thing. Thx for the tip!

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Hi there,
I would like to make a quad manual trigger/gate and i’m interested by the schematic from @analogoutput (Thanks for this). As i’m a newbie in electronic, I would like to know if i only need to multiply by four the schematic to have a quad one. And because it’s untested, somebody could confirm that I’ll not burn off my eurorack modules ?
Thanks !

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I laid it out on breadboard but couldn’t get it working, but that’s about my usual result from breadboarding. I got frustrated and gave up, but I didn’t get angry enough to pull it all apart so I intend to go back to it in the coming vacation.

As for making it a quad, thats pretty much what I was planning to do. Drop the usual eurorack power config into my kicad schematic and then copy-paste that circuit in to make a triple in 8hp, but I am not even off the starting blocks yet…

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Welcome to the forum :slight_smile:

yes

it’s not tested yet, so nobody knows in real life if it works, but considering the circuit and who made it there is very little chance that it will burn :slight_smile:
the best is to test it on breadboard

if it can interest anyone I also made a Manual gate module added with an old rotary dial phone, but by removing this part, you have an adjustable output gate signal from 0 to 5V.

information that helped me here

Thanks !
And thanks again for the answers.
I have tested the @analogoutput schematic with a modification, as somebody told me:
D3 and R8 before Q2, R7+R8=RL=420ohms.
It seems to work fine on the breadboard, 5V output.
Thanks !

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good to hear you got it working, keep us updated how your build goes.

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I think it also depends a lot on the type/color of led you are using.
some are much brighter than others so you have to adjust your resistance depending on what you like (I often use 1k)
happy that work

Not sure what this means, you’ve moved D3 and R8? To where? “Before Q2” doesn’t make sense to me. Anyway R5, R7, Q2, R8 only exist to light up D3, none of that should matter as far as making the gate.