The only clarification i can see is that it needs to be an LM386n-4/NOPB for its 1W output.
Ill build it soon to see whats what (or whats watt ;P)
1 Like
Got a question about resistor subs on the Drum v2…
I’m missing the 430, 470 and 150k and i want to sub for 390 and 150k. is this ok or do i need specific values?
Hello,
I’ve a designed a simple clock with some frequency division - it’s just some basic building blocks kludged together but I’ve built it and it’s worked fine for a while now (worked first time, too, which is a rarity for me!). This is my first attempt at posting any of my work, so I’ve put it here in the unverified section to start, but it this acceptable for the verified thread as is?
Cheers!
3 Likes
If you’ve tested it and it works, i don’t see why not.
Just a note on the stripboard the 100nf caps would be better as close as possible to IC 
2 Likes
Thanks for the feedback! I’ll shuffle the 100nF caps over towards the op-amp on the stripboard layout.
1 Like
Simple and useful, excellent design. What kind of BPM range does it have?
1 Like
Slowest division (‘whole note’) goes from about 16 to 170-ish bpm. That’s just roughly timed as I don’t have a 'scope!
1 Like
I’m whipping up this MIDI to drum trigger module today - thought I’d share the layout here while I build it, I’ll throw the code up once I adapt it from another Arduino I’ve done the same thing to drive animatronics with.
Basically as it says: MIDI input to drum trigger output. I’m going to make them 20ms pulses. I also wanted indicators and the ability to manually trigger each of the outlets with a simple button. Ideally this would be a gate to trigger circuit to drive each one for a nice short pulse, but I wanted to keep it simple and fast to build.
I have the output MIDI jack wired as a proper THRU, not a software thru as I wouldn’t want an Arduino upset to halt the rest of the MIDI chain. I’ll add a MIDI input indicator at some point for sanity checking also.
3 Likes
In your implementation the current the arduino has to deliver is something you have to take into account. What if all outputs are high and all LEDs draw current? Will the arduino be able to deliver or not?
The thing is that in this drawing the resistor values for the LEDs are kinda low, especially if you use modern age LEDs that are very bright. In the old days those values would be OK for an LED, but these days you can use (and I have done this myself) values from 10k to 56k to get acceptable light levels that do not light up the entire room (and reduce the current that is drawn).
2 Likes
Heya - yep that’s been taken into account for sure!
Per pin the Arduino can deliver up to 40ma.
My brain is tired from a long day but from memory this setup is around 16ma per pin so we’re well within safety limits even if they were all on at the same time.
I’m just using basic old fashioned red LEDs, I’m a fan of the muted vintage vibe they bring 
I tested it before I shut down the studio and it was running well. I’ll do some more testing in daylight with caffeine in my system and make sure my code has no bugs and upload the whole lot for others to use.
3 Likes
There’s also total current to consider, 12 x 16 = 192 mA if all LEDs are on. That’s barely under the absolute maximum of 200 mA from the ATMega328P datasheet (and doesn’t even include the current consumed by the AVR itself).
For my current Arduino project the green LEDs I currently use (Tayda A-1553) seem to my eyes to want about 470R. The red (A-1554) about 2k.
3 Likes
Ha! For years I’ve been loading up these little guys to nearly 40mA and figuring on 200mA budget total, but seems not the case, I’ll adjust for a lower current per pin for those LEDs, but so far it’s been going through its paces quite well in the rack.
Of course that’s not to say it’ll fail far sooner than if I wasn’t abusing it.
I also see in the datasheet there’s an asterisk under one of the tables saying to not use more than 30mA per port, and being that ports are grouped, and all of the digital pins are on port 0 and 1 it seems (quick look, I’ll come back to check that) port 1 seems to have 7 pins, and the rest on port 0. That means no more than 4.2mA per pin? That’s pretty nuts. I’ve been going way over this happily for some time… I might have to double check this as it doesn’t feel right.
Also the code seems to be happily bumping along so I’ve come to upload it here, but it seems I’ll have to upload it somewhere and link to it as this forum doesn’t allow for uploads for things other than images
Another quick layout as I strive to get my rhythm section fully in action for some music I’ve been working on for a gig coming up - this percussive snare/hats combo based on schematics from @Dud (SoundBender - thanks for pointing this one out to me - love the sound of it in the videos) and Tiny Dazzler Electronics. Yet to build, but uploading as I zip along here:
Oh and the original schematic from @Dud 's website:
1 Like
It’s not too surprising you’ve gotten away with more than the datasheet says, of course the datasheet’s going to be conservative — but that doesn’t mean you’re not pushing your luck. Bottom line is these microcontrollers really aren’t built to supply power to more than a few LEDs. For that it’s best to use something like transistors switching the current from the 12 V rail.
Hmmm I don’t believe we should restrict to only a few LEDs because of limits, we can play inside those limits otherwise why have them?
I have a work that’s been in operation pushing close to those limits on a very early Arduino from around 2006 since then, it doesn’t run 24/7, but it does run a lot and has done pretty consistently most of these last 15 years.
I think that sometimes we can overthink and overdo the BOM on something like this when really it’ll be happy for longer than it may even be used for (or at least longer than the capacitors are serviceable).
Though I’m fairly new to synth modules, I have been building rough and tumble mechatronics and robotics for many years where sometimes you just have to get it done with a minimal part count or you’ll never finish and I guess I’d like to bring some of that world with me here. When I’ve run workshops teaching teens to build mechatronics I’ve found after a couple of weeks an Arduino with a DC motor hanging off it being directly driven. Massively out of spec, but surviving, so I’m willing to err on the side of taking it to those data sheet limits.
If it works, and it doesn’t burn, let’s not overthink it.
I guess that’s why I’m here in the Look Mum No Computer forum, trying to move a bit faster and focus on making and creating rather than getting too stuck worrying
3 Likes
There’s not that much thinking involved. I don’t mind playing fast and loose with specs especially when the alternative is excessively complicated or expensive, but buffering some LEDs isn’t that. Certainly nothing to “get stuck” over.
4 Likes
Here’s a basic little portamento module I’ve adapted from a couple of others and simplified. I’ve been testing this in Kicad’s simulation tool (ngspice) and getting good results.
This is aimed at 1v/oct applications for nice glide rather than audio/general CV. I found that most designs I found had some oddity with switching or things that seemed strange in the circuit that would alter the ability to track the voltage well, so this one’s aimed at trying to keep tracking super close to input voltage.
Will build this later this week to test out.
Hope it helps others:
7 Likes
Be interested to see how it works out. In your sims did you see linear or logarithmic type slews on the output?
Cheers
1 Like
This is where you suddenly realize a portamento and an AR envelope generator are more or less the same thing.
2 Likes
