Hey what is the most simple way to make a very bare bones gate/trigger circuit? Literally just a button to trigger a gate/trigger signal to a module? Does anyone have a circuit that can do something like that or some kind of idea?
I just made one of these the other day! One sec, I’ll share…
It’s stupidly simple. Eurorack power header, the +12 goes into a DC-DC step down to make it +5V (you can skip this if you have a 16 pin power supply and header with a 5V rail), which goes to the input of the button, the output of the button goes to the tip of the jack, there is a 1M resistor between the tip and the sleeve of the jack, and then that goes back to ground. Works to trigger my kick drum module.
6 Likes
That could be just a voltage divider. 10k and 6.8k resistor for instance.
1 Like
That’s almost certainly true, I just got a bunch of these little chips for something like 10 cents on AliExpress, and wanted to try them they’re neat. You solder one junction to get certain values, or you turn the little screw to get a custom amount.
1 Like
Re-creating a seminal moment in the development of the Moog synthesizer
2 Likes
I actually found a somewhat simple circuit as well last night, although I’m using a 9v battery to power it and there’s a 470 ohm resistor between the button and the tip of the jack socket. Is 470 ohm a good amount or is it better to go a bit higher? I will share the schematic because I think it is way more simple and was hoping if anyone takes a look at it, maybe we can add a lot more improvements and such to it.
With 470R you’d get currents of around 20 mA while the jack is shorted. Assuming that’s a brief thing while a plug’s being inserted or removed I’d think that would be fine.
But you do need a pulldown resistor between tip and ground. Otherwise when the switch is open the tip is floating, not 0 V, and as @BlackDeath can tell you that won’t work reliably.
Once you add that, it’s really about the same thing as the solution above. Only remaining difference is there’s nothing to reduce the voltage so the gate voltage is whatever you’re powering it with, 9 V if it’s a battery. If you want a 5 V gate add a voltage divider, maybe 1.2k on top and 1.5k on bottom.
1 Like
Hey maybe you can try this! I have build it and it working good !
http://familjenronnberg.se/~niklas/diy/eurorack/manual_gate/
There are 3 gate mod:
- a basic manual gate with a push button
- a manual gate with a spdt switch for an holding mod.
- a manual gate with an envelope control (attack/decay)
I have redraw the schematic for a basic manual gate:
It was my first build :
4 Likes
What is the purpose of the first transistor stage? Seems to me normally you’d use that if your input were a voltage coming from something that couldn’t source much current or that was not the full rail voltage, but here it’s a push button on the rail — the same source the transistor switches. So what’s the reason for it here?
I think the first transistor stage is to generate the gate signal and the 2nd is for the LED.
1 Like
My point is the gate signal could just be the 12 V from the switch, couldn’t it? (With a current limiting resistor and a pulldown.)
1 Like
yep. on the other hand… transistors were cheap so… 
1 Like
You are right ! Sorry I can’t explain this I’m really not a good enginer, but it working good !! However I’m often see this configuration in many designs who using gates.
I have find this too
Google brought me back here whilst looking for a gate button schematic. I am eager to give the one from @saint_et_moudulard a trial on breadboard but I dont think I have any 2N2222 transistors in the stash. Is there a range that would do the same job so I can avoid making a component order?
2 Likes
BC547 , BC548, 2N3904, i think
2 Likes
Yes, any general purpose NPN.
2 Likes
I have all of the suggestions, so I’ll give it a try tomorrow now, thanks!
1 Like
As @analogoutput mentions above, you don’t need a transistor at all, the switch has plenty of drive by itself. It can even drive the LED directly no need for a transistor buffer there either.
See @Jewceman’s post above.
2 Likes
thanks for that, I have been so busy with work I haven’t had time to try anything yet.
I was initially interested in the module LMNC uses in his Kosmo rig, but thinking about it, that must also accept a gate input as it flashes along with inputs as he plays. Is there a simple way to add that?