# Simulating keyboard strokes with shortcut key combinations

I rigged up a tiny little project using a scrap Dell keyboard, where I tore the keyboard apart and salvaged the USB control board. The actual keyboard is gone. Then, I traced the circuit for the "Enter" key on the keyboard, to figure out exactly which combination is needed to close the circuit to trigger "Enter", and hooked up a single button to it.

This works great, and I could presumably do it with any button.

However, I'm also interested in key combinations. For example, CTRL + SHIFT + R. All 3 of these circuits can't be closed at precisely the same time - CTRL + SHIFT needs to be triggered before the R key. So the same idea of a single button directly connected isn't going to work.

NOTE: I have relatively little knowledge of circuitry design, but have played around with it plenty.

What's a circuit I could easily create which can simulate this? I assume it should be as easy as a slight delay between closing each circuit, but I have no idea where to begin creating a circuit.

Ultimately, the end goal is to create a custom button panel where each button sends a key combination to this scrapped USB keyboard controller to simulate keystrokes.

To add a little more details, in case you're not familiar, the keyboard works like this (at least the one I'm using). The board has 27 contacts which are pressed against the actual keyboard sheets. 1 contact (AFAICT) is a ground, then there's a group of 8, and a group of 18. When a key is pressed, it closes a circuit between one contact in each group. So, for example...

[GND] - A B C D E F G H - 1 2 2 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

The "Enter" key is achieved by closing a circuit between E and 7.

I'd like to avoid any sort of microcontroller if at all possible. I recall in the past, seeing a trick with a capacitor and transistor, which could achieve a delay.

• Upon further study, I believe it might be possible with a Zener diode, capacitor, and transistor. A Zener is designed to allow certain amount of breakdown current to pass through the other way, and charging a capacitor until it reaches that breakdown voltage might be able to simulate a delay. Might require another diode to capture the negative current though. I have no idea how to actually design such a thing though. – Jerry Dodge Feb 4 '18 at 17:40