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

Hey all!

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

(PS originally posted in the Hacking section, but prob more suitable here)

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 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? Something along the lines of the left part in this schematic: http://www.ermicro.com/blog/wp-content/uploads/2008/12/trsw03.jpg

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

Pleeeeeeeeeease somebody help! :sweat_smile:

Hope i've explained the situation well enough, if not i can rephrase?

Thanks

Jordan

jordan_ellipsis: Pleeeeeeeeeease somebody help! :sweat_smile:

Hope i've explained the situation well enough, if not i can rephrase?

Jordan,

I think you've explained the situation quite well, but somehow the point of the whole exercise is lost to me. Connecting random parts of some gadget together without any knowledge what one is doing just doesn't sound like a productive activity.

Considering that you have no idea what you try to switch, it makes little sense to offer any advanced solution how to do it. Relays are probably safe as you won't deal with much current and low voltages. If you want to know how to drive those with an Arduino, look at the solenoid and relay tutorials. The explain quite well how to attach them to the Arduino.

Korman

I think you might get a better response in the Device Hacking part of the forum :- http://arduino.cc/forum/index.php/board,17.0.html

Just remember to connect all the grounds together and don't feed more than 5V into the arduino.

Korman, i do know what happens when the two parts are connected tho! It causes the image to be modified. This is why i want to connect the two points together. I want to be able to turn the glitch effect on and off. So we go from normal image to glitch image to normal image etc. If I can control this from the arduino (using max/msp) i can write a program which automates the turning on and off of the glitch. I plan to use the output as a visual backdrop during an electronic music performance.

Normally, in circuit bending, you would just solder a toggle switch in between the two points. But i want to use a transistor instead, which closes the circuit when it receives a +5V from the arduino.

Mike, should i connect the ground from the ardunio to the transistor AND directly to the ground for the NES? Or will the transistor already be connected to the NES ground just by connecting it to one of the bend points on the circuit board?

If the point you are trying to bridge is floating above ground then it is better to just connect the transistor across the points you want to bridge with the emitter at the lowest point and the connect the grounds of the arduino and the hacked device together.

Sometimes you might have to use a logic level FET in place of a transistor because that mimics the action of a short circuit better. That is important if the points you are trying to bridge are carrying audio signals where there isn't one end that is consistently lower than the other. Transistors are only really useful for the shorting of points with fixed DC voltages on them.

It might be easier for you to use a 4066, that is logic level and will allow you to short out 4 points but unfortunately all at the same time. However a 4053 will allow you to short out one point to any of two other points, also check out the 4051.

Thanks for the continuing help!

How would I know if the points I want to bridge are "floating above ground"? Is there a simple way to check if one point is lower than the other e.g. using a multimeter? Also, am I checking for current or voltage here?

I popped into an electronics store today and picked up what I could from their limited selection. I got a 5Vdc 2 amp SPDT relay & a 12Vdc 5A DPDT relay. I couldn't find any SPST which seems more useful to me in this situation. I also picked up a few 2N3904 transistors and a few BD136 transistors. They had no Darlingtons. tbh, i guessed at which ones to buy. Should I try this with one of those transistors first, before moving to a relay?

I originally looked at the 4066 chip; hmm the 4053 does sound useful. Are circuits using these kind of chips easier to assemble? Would you have a rough idea of how to set this up in my case?

I am really appreciating this support; i wish there was a way to pay you back! I'll post some videos of this stuff/the performance if it works - you might like it!

Is there a simple way to check if one point is lower than the other e.g. using a multimeter?

Best way is with an oscilloscope as you see if there is any AC on the lines. If you don't have one then make the arduino into one, there are lots of versions about.

am I checking for current or voltage here?

Voltage.

? Would you have a rough idea of how to set this up in my case?

Wire up the power rails, wire the control inputs directly to the arduino outputs and wire the input and output to the points you want to short. Again connect the rounds of the two systems together.

OK thanks for that, I'll try to get one of they chips and give this a try.

Would something like this darlington transistor array also work? http://uk.rs-online.com/web/search/searchBrowseAction.html?method=updateShoppingCart

For any of these chips, would i still need to add resistors (or anything else) at certain points in the circuit?

Well that link was to your basket and as I am not you there is nothing in it. A Darlington is just a transistor and offer you no advantage. There is no need for resistors with the multiplexer chips. With transistors you need them in the base.

Dammit, sorry my bad. The link should of been this http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=652825A&x=0&y=0

OK it seems like multiplexer chips would be a good solution for me given my lack of knowledge. I'll start reading up on them and try order some online. Thanks!