Circuit Bending Nintendo (NES) - Use transistors as switches?

Hello lovely people of the arduino forum!

I'm currently circuit bending an original Nintendo Entertainment System (the one from the 80's). For those unfamiliar with circuit bending, it's basically when you expose the circuit of a device and create short circuits in arbitrary places in the hope of corrupting it's functionality. Commonly performed on cheap, battery-powered kids audio toys. It requires no experience in electronics to start 'hacking' at an elementary level, which, unfortunately, is the category i fall into You flip the circuit board over so all you see are the solder blobs, and use crocodile clips (or jumper wire) to connect various 'blobs' together, therefore forcing a change in the circuitry, and often resulting in crazy outputs! Kids toys can end up screaming with distorted, alien voices... it's very fun.

So i've been applying this methodology to the NES. When i connect certain points together, the image glitches, see an example here: http://www.art-rash.com/pixelform/videobends/NES/images/nes-build-010.jpg The standard practice would be to connect two 'bend points' together using a physical SPST switch, so the glitch can be turned on and off.

But I'd like to control these switches from a Max/MSP patch, using an arduino.

I've been researching this like mad, and was initially advised down the route of using a relay switch. But the more I read, the more it seems like a transistor is the tool I need! I would use a digital pin from the arduino (in output mode) to send +5V to the transistor, therefore closing the switch and activating the glitch. Does this sound like the right idea?

I know this is probably an extremely basic circuit, but could someone help me with the schematic? And also the correct transistor to use, along with any other necessary components?

I have vague ideas of how to go about setting this up, from what i've read. But i'll omit them just now, so I don't confuse things.

I realise it's frustrating dealing with someone with limited electronic knowledge, but I'm willing to listen to/read/learn whatever is required to make this happen! It's probably so simple, but I really couldn't find anything online about using arduino boards to activate bend points on circuit bent instruments.

Thanks,

Jordan

Just some extra info here, the power supply for the nintendo reads:

INPUT AC230/240V 50Hz 17W
OUTPUT AC9V 1.3A

Can this information be used to calculate the value of the transistor needed?

From my knowledge so far, i'd want to connect the digital pin output from the arduino to the Base of the transistor with a 1k resistor in between. This would 'control' the switch.

I'd connect the collector to one of the bend points (point A), and i'd connect the emitter to the other bend point (point B). So when the switch is closed, current runs from bend point A to bend point B thus activating the glitch.

Is this sounding right so far?

I then am little confused as to where to connect the power and ground of the arduino. Do i connect the ground to the emitter, and also to the ground of the NES? And then connect the power to the collector, and also to the 9V from the NES?

Please please help if you can!

Jordan

I then am little confused as to where to connect the power and ground of the arduino. Do i connect the ground to the emitter, and also to the ground of the NES? And then connect the power to the collector, and also to the 9V from the NES?

You don't connect ground to anything on the transistor, or the power to anything on the transistor. To use the transistor as a switch in its simplest form you need to saturate the transistor when its on, and have it at cutoff when its off. Basically, data pin through a resistor to the base like you said, and each contact of the "switch" would be an emitter or collector.

The thing you need to find out is what current you need through the base to get into saturation, which depends on your specific transistor, and not to exceed the Arduino's max output current.

Although, that said, transistors can't switch AC voltages. You said the power supply is 9V AC, so that might be an issue. That's probably why a relay was mentioned.