Introduction: Atari Punk Organ, a Simple 555 Synthesizer
This is my Atari punk organ, it is a 555 timer piano run through an Atari punk console monostable generator, the piano is based on another instructable I made: https://www.instructables.com/id/How-to-make-an-electronic-piano-with-a-555-IC/
it has 2 speakers which both play different sound at the same time, which makes an interesting sound and it is tunable using the trimmer potentiometers so you could in theory make an accurate scale, the notes are also layed out like on a piano.
Another feature is a potentiometer that controls pitch bend and a rotary switcjh to change the capacitors on the organ, changing the sound.
Step 1: Video
Step 2: What You'll Need
What youll need to make this:
2x 555 timer chips
10k + 100k potentiometers
20 2k trimmer potentiometers
10n, 100n, 47n and 2 10uf capacitors
large perfboard (or you could make a printed circuit board)
assorted wire and battery clip
glue, cable tie and cork
probably desoldering pump/wick
screwdriver for the trimmers
Step 3: The Piano Circuit
The piano circuit is based of a circuit diagram made by Collin Mitchell, the keyboard is connected through pin 2 and pin 3 goes to both the speaker and the atari punk module, I used jumpers on both sides of the perfboard and attached the battery clip to the 1 and 8 pins, i used hot glue to stop them breaking from stresses due to movement, the speaker is glued to the bottom of the boardwith bostik and acts as one of the legs.
The 100n capacitor is replaced by the rotary switch, with three capacitors connected. the wire from 6/2 goes to one of the middle termnals and other capacitors you want to use are connected to the other terminals of the switch and to ground. I used 100n, 47n and 10n capacitors but you could use more different values.
Step 4: The Keyboard
Making the keyboard needed lots of soldering, the trimmers replace the resistors in the origional diagram and the left and middle pin need to be soldered together, you could make a bridge using solder but i found it was quicker to use the leg of a resistor i cut of from anaother project and saved. The switches i used have 2 pins that are allways coneced on either side, i soldered all the connected pins on the bottom together to make a long unbroken line which is connected to pins 6 and 2 on the 555. when a button is pressed it conntects pin 7 to 6/2 and all the resistors before the button was pressed add up their values and that controlls the pitch
The top layer of buttone is set out like a pianos black notes so there are larger gaps between the bases of the buttons, so instead of using solder to birdge the bases i used a piece of wire that went to each button and the pins 2/6. The green wires are where the bottom layer is sonnected to the top, look at the 5th picture to see where they go as it is hard to explain.
Step 5: The Atari Punk Module
follow the schematic for the second monostable half of the atari punk console, connecting the ground to the ground on the piano ic and the power to pin 8 through a switch so it can be turned of if not wanted in the music. Pin 2 is connected to pin 3 on the piano ic with a jumper wire under the board. I used a 100k instead of a 500k pot. as i think it makes a better sound and i put it on the left side to the board although I would recommend that you put it next to the other potentiometer so it is easier to play with one hand, I glued the second speaker to the top of the board and to make it neater I put the wires from the speaker down into the board and connected them to pin 3 and ground using jumpers under the board
EDIT: the picture is not mine, it is from http://www.robthefiddler.com/
Step 6: Finishing Off
I am using the piano speaker as one of the legs so I used a wine cork that i cut at an angle and superglued that to the bottom of the board, im sure there are more elagant solutions but i think it looks quite good.
you could make an enclosure but im not sure how you could mount the buttons unless you made the whole thing completely differently, I like it without an enclosure. I put hot glue on the bases of the potentiometers to make them more stable and easier to use with your little finger while playing the keys with the rest of your hand, it you put both potentiometers next to each other this would not be necessary. i used a cable tie to attach the power cable to one of the holes in the perfboard and glued the switch and speakers on with bostik.
I power it with 4 AA battery which produce about 5v and make it loud, a 9v is ok if your just using the keyboard but it isnt usually powerful enough for both 555s.
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