Comments on: mini space rockers

By: steve

steve — Sat, 13 Mar 2010 03:05:02 +0000

Thanks AGAIN Eric! Just built a bread board version and it works a treat! About to see if I can make a 4 voice sequenced version… a Mini Space Rocker Drum Machine. I shall keep you informed.

By: JR

JR — Sun, 24 Jan 2010 18:14:11 +0000

Hi Eric,

Cool circuit. I have a couple of questions/comments for you.

1. If you are using the button as the trigger, can you simply charge C3 right thru the button?

2. If you use MOSFETs for the charging circuit, then I think you can probably eliminate the voltage dividers because you can just pull the gate of the n-channel all the way up to the (+) rail and the gate of the p-channel all the way down to gnd. Thoughts?

Love this stuff man! Glad your designing it!!!!!

By: empaschk

empaschk — Thu, 14 Jan 2010 19:25:11 +0000

Transistors:
BC549B x 3
BC559B x 1

Diodes:
1N914A

Resistors:
100 kOhm x 2
33 kOhm x 3
22 kOhm x 1
10 kOhm x 3
220 Ohm x 1

Capacitors:
1 uF electrolytic
10uF electrolytic
C1,C2: Tune (2.2 nF - 220 nF)
C3: Decay (1 uF - 10 uF)

By: admin

admin — Thu, 19 Nov 2009 22:49:05 +0000

rrob: the NPN-PNP pair is a charge dispenser. when you trigger the circuit, this pair drops a measured charge of electrons into C3; C3 then becomes the power supply for the oscillator. The envelope of the sound is generated as the circuit dies by depleting its available energy from C3. Its like charging a tiny battery and letting the oscillator drain it.

-eric

By: rrob

rrob — Wed, 18 Nov 2009 06:45:14 +0000

Very very neat…. May I ask what the Npn pnp pair is for?

By: admin

admin — Sat, 31 Oct 2009 21:37:21 +0000

I used BC549 / BC559 because I use them for lots of other stuff. I think you could get away with using any medium-gain bipolar transistors.

2N3904 / 2N3906 should work, but be sure to look up their pinout because it may be different than BC5xx.

PS I get parts from mouser.com.

good luck building!
-eric

By: chris

chris — Sat, 31 Oct 2009 17:17:02 +0000

Johan - there’s a small but important mistake in your parts list.

only 3 of the transistors are BC549 (NPN). The other is BC559, which is PNP.

By: Johan Larsby

Johan Larsby — Thu, 29 Oct 2009 19:51:02 +0000

Transistors
bc549b 4pcs

Condensators
c1 1pcs
c2 1pcs
c3 1pcs
10u 1pcs
1u 1pcs

Battery
9v 1pcs

Trigger
(button) 1pcs

jack or line 1pcs

Resistors
10k 3pcs
33k 3pcs
100k 2pcs
22k 1pcs
220 1pcs

Diode
1n914a 1pcs

I think this might be correct.

By: mubo

mubo — Thu, 29 Oct 2009 17:59:17 +0000

could you use 3904/3906 transistors instead?

thnx

By: Will

Will — Thu, 29 Oct 2009 15:07:39 +0000

… or maybe that should be from the cap to ground… I didn’t do to well in intro to circuits.