MY plan was to make it into a eurorack size module but I ran into a couple problems with the sizing of things so its ended up as in a stand-alone box and is running off 9volts.
Has any one built one of these before? I’m having a bit of trouble with the trigger output. If I plug in headphones to the trigger out I get some constant clicks so it seems to putting something out (HOORAY) but when I plug it into my LMNC sequencer its not moving things along. I have found though that when I put it through the LMNC super simple mixer things start moving!
So thats made me start thinking that the TL072 is doing something to fix up the signal. Problem is I cant seem to work it out. Ive tried bashing a couple things together but still no luck. Also does the TL072 require the -12volts? I think it does to work properly right? Is there something else that I could use instead of the TL072 and keep it at 9volts? Anyone got any ideas?
What’s inside the box? What’s the trigger jack connected to?
It’s possible to use a TL072 with +9 V and 0 V but not very good — you can only get a couple volts swing around 4.5 V out of it. If you have to use such a power supply something like an MCP 6002 is a better choice. It’s rail to rail meaning its output can go pretty much 0 to 9 V.
The BleepDrum has a trigger output pin on the board, the jack connect directly to this and to ground. Theres a bit on info about hooking up the trigger inputs, I havent looked into this yet as the trigger out is more useful to me at the moment, on the Bleep Drum guide
I found a couple other people (heres one) who had built Bleep Drums as eurorack but they dont seem to have the trigger output working yet either.
Inside the box is pretty empty, just the jacks and space to eventually add whats needed for the trigger outputs, I think they need to be inverted thats in the guide above too. The box makes it feel a bit more sturdy than the pcb on its own. plz excuse my too long cables all bundled up.
OK, so it’s an ATMEGA328 powered by 5V and you’re connected directly to one of the output pins. Which by the way is kind of dangerous (to the ATMEGA328), if you plug it into the wrong thing you can fry it. But until then you should be getting 5 V triggers on that jack. Which is plenty large enough to trigger the LMNC sequencer. So at least in principle you shouldn’t need to condition it with an op amp (though doing that would protect the module’s ATMEGA328).
Since you talked about diagnosing with headphones I infer you don’t have a scope you could look at the output with, which would make things easier. You could verify the trigger really is 5 V and find out how wide it is. As it is you’re flying kind of blind.
The green module is the super simple mixer? Weird. That shouldn’t increase the amplitude, or the width.
The one thing I can think of is the problem might be with the sequencer, not the drum module. You built it as shown in Sam’s writeup? One problem with his design is the pulldown resistors on the input jacks are connected on the wrong side of the diodes (they should be between the diodes and the Arduino, not between the jacks and the diodes). That can lead to flaky behavior. Why it would respond one way to the direct trigger and another way to the trigger put through the mixer I don’t know, but that’s kind of what “flaky” means. I guess the sequencer and mixer have a good ground in common; in principle so should the drum module and the sequencer, via the cable, but maybe not?
no i dont have a scope, just a terrible multimeter that isnt giving me particularly nice readings, I think this is because of it pulsing rather than a constant rate.
yeah that green module is the super simple mixer and fixes it. I’ve also plugged it into one of those pt2399 echo modules from aliexpress and that fixed it as well, i dont know if thats any help…
Bleep labs have provided this circuit for adding the trigger ins
could switching things around a bit potentially work? I’m sorry I know we are talking a lot in hypotheticals
as for the sequencer, yeah I’ve gone through the posts on here about that and got it mostly fixed. I am able to use a clock or lfo as a trigger for the sequencer so I know at least that part of its working correctly.
I’m not sure that will do what you want, as it basically acts as an inverter i.e. If, referring to your second diagram, you have 0 volts on the input labelled “trigger out from bleep drum” your NPN transistor will be “OFF” and the “trigger output” will be pulled up via the 100k resistor to +5V. When you put some higher voltage, anything over 1V really, your transistor will be “ON” and it will pull the “trigger output” to GND, which is probably the opposite of what you want.
I had a bit of a dig in the code, and if the comments are to be believed, then it runs at ~15kHz
/* Enable interrupt on timer2 == 127, with clk/8 prescaler. At 16MHz,
this gives a timer interrupt at 15625Hz. */
And - I think the trigger out we’re talking about is pin 2 on the header, right? Which should be D12 on the schematic.
So, that should be triggering for at least 80 * 1/15625 = 5ms, which should be enough to trigger somethings, but could maybe be a bit longer?
Also, loopstep has to be different from prevloopstep - but I’m not sure what the code is trying to do where that can happen - it all gets a bit janky 'round there… something to do with recordmode being on and miditempo off and, if I’m reading the code correctly some use of uninitialized variables.
Yeah that’s the other one that I had been looking at but couldn’t find the link when I made the original post. It’s probably a good idea to have all the references in here though thanks
It looks like that guy has some other problems going on. The record and playback is working fine for me.
I’ve been getting some emails back from Dr Bleep and we are trying to sort it out. He suggested adding a delay or anything to that part of the trigger code is a bad idea as there’s other wacky timing things going on.
But it also appears that I’m getting some weird voltages out of the other pins, things that should be low are high etc.
I was hoping to use this guy as the master clock but now I’m thinking that it might be better to sequence it with something else instead. It would be a bit of a shame though. The internal sequencer is quite nice and records the pitch changes which you’d lose with an external sequencer.
I’ve been talking with Dr Bleep and have fixed the trigger output issue. We needed to build a little circuit which sorted it out, I’m not that technical (clearly) but from my reckoning its taking the weak Bleep Drum trigger output and replacing it with a stronger one powered directly from the battery.
Just curious, what voltage do you measure on pin 4 (nominally +5 V?) I’d expect the trigger amplitude to be the same and even if it’s a little under 5 V I’m very surprised it doesn’t trigger the sequencer. The threshold for a digital HIGH signal is only 2.6 V and surely your trigger amplitude (without this mod) must be larger than that. So I am confused.
Your schematic says +12 V Pin 11 on Header but pin 11 is +9 V. Either way, sending more than about 5.3 V into the sequencer’s Arduino Nano (ATMEGA328p) input pin is better avoided if possible (there are protection diodes, but I don’t like relying on them), but 9 V is better than 12 V. 5 V from pin 4 would be even better, if that works, but as I said I’d expect the trigger amplitude and pin 4 are the same already, and larger than 2.6 V. Very strange.
I’m getting a bit over 4v from pin 4 (if I remember correctly) but from pin 2 (trigger output) I was only getting around 0.6 volts. This is what my multimeter is saying and probably way off since the signal is too fast for it to read properly. I’m looking at getting a scope ASAP!
The 12v is just what Dr Bleep put on the schematic when mocking it up. its coming out 9v directly from the adapter that Im using. you are right though I could switch it over to the 5v output from pin 4 and it should work the same.
But end of the day, it works for me (for now) so Im happy
Did you just get the PCBs from the Bleep labs Github? Thats what I have and are totally fine. You need to build other circuits for the trigger inputs as well anyway so slapping some stripboard on at another level is good anyway.
I should also add that I did get a acrylic panel laser cut for this as I wanted to have it as a eurorack module initially. stacking stripboard behind that would be no problem either. But I found that the holes for the buttons, although there was enough room for them to breathe, were still a little tight, if buttons were pressed down when its powered on it was doing funny things like being stuck in record. The box just made things a little more convenient for me. Its probably more of an FYI to give a bit more space around the buttons like in the links above where people have built euro modules.
nah i got the ones from the repo of the attepted eurorack convertion by L71 (didnt read the descrition fully before sending off the gerbers)
Once i get rid of my backlog of other PCBs on the bench I will attempt a bleep drum again, but with these lockdowns and my son not going to school at the moment, that’ll maybe be 2025…
