Let's Make Robots!

hacking toys

hey all,

i'm trying to take apart a bunch of toys and other small electronics. They all have a push-button that mashes down on the PCB to operate. the spot underneath the button looks like this: (forgive the hasty visual):delete-me.gif

I think that the push of the button connects the two. So my question, then:

What's the best way to get "electronic-ize" this so my IC can do it?

Possibilities:

-solder them together and turn the power on/off via my IC?

-connect the negative to an outpin (and transistor) and fire away?

-other?

I could experiment, but I would have to sacrifice a toy or two, so I'll ask my fellow robophiles ...

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In the case of the button relaying a unidirectional control signal, you might be able to track one of the leads to Vdd or ground, where the other lead probably goes into the toy's main chip. If you can identify what the 'closed' state connects the chip to, you could connect an output from your controller IC to the chip side of the button and use easy high/low digital signals to emulate the pressing of the button.

Often times these types of contacts are part of a matrix keyboard made up of rows and columns.

Using a transistor may not work because the polarity of the signal accross the switch changes with

each scan. In these cases, a bi-lateral switch IC is the answer. You can use a quad unit, (4066) to

provide a direct interface between your micro and your toy circuit.

If you google "autofire for XBOX", there are good examples of doing this.

 

If you have an old computer keyboard, they usually have these type of connections under the keys, then you could take that apart instead of the toys, but another solution would probably be best, as this is still destructive to other things.
If you know the polarity of the connections (try checking with a multimeter with the power on) then a transistor should work fine. Have your picaxe output drive the transistor by a 4K7 resistor.
you mean put the resistor between the axe and the transistor, or between the transistor and the toy?

I would say that the switch is basically shorting the two sets of contacts together to make the circuit.  I have seen elsewhere that the electonic way to do this is to use a FET with the drain and source to the contacts and then use the IC to trigger the gate.  You will need to determine polarity of contacts and power through them.  The original source was for a PIC controlled trigger for a video camera for RC aerial photography if memory serves me right.

 

Pete