Close keyboard contacts from Arduino

Projects Discussion and Showcase Device Hacking
1

Hi!

I need to control a system wich have a keyboard from Arduino, simulating the push of its keys.
How can I close the contacts of the keys from Arduino? Using an optocoupler?

I do not know if I can use an optocoupler, and if where possible, wich model to use.

Note: I measured that when I push a key in the keyboard, its contacts aren't closed with a 0 Ohm resistence, but they are closed with about 55-75 Ohm.

Any ideas? schematics? Has anyone tried it?

PD: I attach a picture the keyboard contacts

Thanks!

IMG_20130526_020844.jpg
IMG_20130526_020844.jpg465×502 76.6 KB

2

what voltage is the device

could use a transistor, collector on non common pad, emitter on ground, 1k to base with the arduino on the other side

3

Thanks Osgeld

The device voltage is about 3.5v - 5v.
You suggest a simple NPN ? like a 2N2222???

The common pad is not ground. The pads make a matrix with common on columns and rows (like the attached image).

Your suggested solution can work properly anyway?

howkeymatricesworks_1277635652.png

4

Or a bunch of little relays. Here's a 1284 driving 15 relays, design had 18 originally, 3 were removed for some other expansion.
USB and RS232 interfaces.

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5

Thanks CrossRoads for your suggestion. Simple to develop, but my circuit must be installed inside other device and I haven't space to place about 14-15 relays :slight_smile:

I readed the datasheet that sais Telecommando, the CD4066. Seems an interesting solution, but for simplicity and availability of components in my city, I prefer using a few simple optocoupler. Do you know any recommended model? Can it be a valid 4N35 or TIL116?

Thanks!!!

6

given your image you could do it with 16 transistors, theres a common ABCDE and 1234

given the jack squat current configurations for this type of layout you could accomplish it with a transistor array in a dip format