clapclap 1386

Last update: Sat Jan 10 23:04:53 2026

This is the ATtiny13 and LM386 version. You can check also the Clapclap 2313 which is based on ATtiny2313 and a Holtek HT82V739, or if you're really curious the original one Clapclap with ATmega328.

Changes compared to previous versions

Compared to the original Clapclap 2313 here are the main changes:

Components change of course :
- Attiny2313 ⇒ Attiny13 : 8 pins package, just enough, but needs a few jumpers if you want to program it (see below)
- HT82V739 ⇒ LM386 : easier to source over the world but requires a few additional caps
Added reverse polarity protection on 5v VCC (can bypass, just put a wire)
Added a cheap Zener diode voltage ref to protect from overvoltage (can be ignored, leave open)
Added a fuse/resettable fuse on the HOT side (can bypass, just put a wire)
Larger trace for main but still keeping distance between traces (can drive more power more safely, still keep it under 100W)
Leds can be SMD leds instead (both through hole and SMD are available)
Microphone is now on the farthest side of the main, to minimize the EMI
Adjustment potentiometers are on the side of the board, easier to adjust if you put vertical potentiometers
NPN transistor pinout on the board (E-C-B), easier to identify equivalent part

What's inside / Parts list

ATtiny13
LM386 opamp
A electret microphone
A relay (my case 5v that drives up to 5A/220V)
A NPN transistor to drive the relay　２ＳＣ２１２０－Ｙ
- Can be replaced by any NPN transistor with pinout [E-C-B] (front view, left to right)
A flyback diode and a few reverse polarity diodes
A few resistors, caps, potentiometers,...
- C1 : 1uF
- C2 : >= 1uF
- C3 : >= 0.1uF (optional cap, just leave open is ok)
- C4 : >= 4.7uF power rail stabilizer, can go as big as 470uF no problem (optional cap but strongly recommended)
- R1,R2 : 100ohm-1kOhm to limit current for the leds

Assembly

By default you should program your Attiny13 and then put it into its IC socket, and you're done.

No programming after assembly

If you don't plan to program the Attiny13 after you put it in the board:

Solder (close) all the surface mount jumpers J1, J2 and J3
No need to fill the ISP programmer or the jumpers J1, J2 and J3

Programming after assembly

You put everything into place, and then you decide to change the timing of claps, or you want 3 on the row, or you want to make an auto-turn off ... whatever, you want to change the code, and you want to do it on the board ('cause you're cheap like me and you skipped the IC socket). How do you do that ?

Open the SMD jumpers J1 and J2 if you closed them (a piece of solder wick and iron and you're done)
- J3 can be left closed or soldered
Solder the ISP programmer and the jumpers J1, J2 and J3
Plug your programmer on the ISP and remove the jumper J1-J2-J3 if any
- Do the programming magic
- In order for the circuit to work you must close the jumpers J1-J2-J3 (permamently by soldering the SMD or temporarily by puting a jumper on the connector)

Putting and removing the jumpers is a pain in the neck, but that's the price to pay of having a small micro controller, I had to share pins for many functions. Is there a better way to design this ? I'd be happy to hear that so please teach me.

Code

On GitHub.

Board

Max power

The power max the bord can drive is (according calculations here), is about 4- amps (making a 10 degrees temperature raise):

1 oz.feet^2 copper

1.93 mm width

about 20-30 mm long

You don't want the system to drive so much more than that, so be safe, or double up the wires with bigger copper wires.

Schematics

On GitHub too. Look at files Clapclap1386.*.

Points of interrest

Compared to the Clapclap2313 version, a generous part of the code was rewritten, such as the general logic of the program.
All the job is done with interrupts, main code is just an empty loop:
- One interrupt counts hundredth of seconds and keep a rough idea of time passing (so it can validate that 2 claps happen in the predefined timespan)
- One interrupt is triggered when the comparator detects that the mic input (post amplification) goes higher than reference voltage (MIN_LVL potentiometer) and saves the clap time

Alternate version : a smart footswitch

Replace the mic by a cheap footswitch, drop the LM386, a few airwires. Now the switch turns on after a long press only, and turns off on a simple click (for safety).

Code (Eclipse project) on my GitHub repo.

Pictures

Board assembled without the relay though. Working fine, just J1 and J2 needed to program it.

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