Audio Waveform Generator
Description
This Audio Waveform Generator appeared in Maplin Projects Book - 48 (PDF of article included). I created my own board using eagle software (eagle files included) and used OpenScad to design a suitable case for it. The board shown in the image is my first attempt. The V2 board included in the associated files fixes the problems of the Frequency pot being wired back-to-front, the capacitors C13-C16 hitting the nut that holds the attenuated BNC socket, moved the power connector because it was hitting the battery holder and added notches for the cables from the BNC sockets. The 4 trimpots are soldered on the back of the board so they can be adjusted easily. The power and output connectors are also on the back of the board. I used 1/8W resistors throughout to keep a 7mm hole spacing. You can use 1/4W but they will be a tight fit. ________ Assembly ======= For the PCB mounting posts, drill holes out with 2.5mm drill and create a thread with a 3mm tap. I used 6mm M3 screws to hold the board. Some of the other holes for the buttons and pots may need drilling out or filing to make them fit correctly. The supply requires two 9V batteries providing a positive and negative supply. The power switch needs to be double pole single or double throw. Put the switch between the +9V and -9V supply leads. The 0V or common lead does not need to be switched. I suggest soldering the LEDs in place after you screw the board onto the front panel so you can push them hard up against their respective holes. The pots proved difficult to source. You need pots with long shafts, the standard 15mm shaft won't work. I got pots with 20mm shafts but even these required knobs that don't have a gap between their base and start of the hole. I got my pots from speed_mart on ebay (https://www.ebay.com/sch/speed_mart/m.html)
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