[SOLVED] Star Wars - R2D2 Cake for Nephew

[HvEdtg83]

I'm trying to figure the easiest way to wire up a R2D2 cake we are making for my nephew. The electronics would be worked into the cake and insulated from it.

I would like to have a button that he can push which would simultaneously trigger a red LED (mounted in a bezel) and initiate a 9V sound recording module (from Radioshack) that I would use beforehand to record the R2D2 sound effect from one of the movies.

Ideally the red LED would come on and stay on, and the recording module would play back only once unless the button was pressed again.

I'm thinking it can be done with
- battery + battery holder
- recording module
- resistor
- red LED + bezel
- on/off push button

Would it be possible for me to wire up the recording module as normal and simply insert the LED portion of the circuit in between the battery and the recording module?
Any advice is appreciated

 

[BradtheRad]

Here is a link to Radio Shack's description. It says the module comes with a speaker, 9V battery snap, and push button. Customers give it favorable comments.

https://www.radioshack.com/product/index.jsp?productId=2102855

You push the button momentarily. The device draws power for 20 seconds and plays a sound. (It may be wise to disconnect the battery when you are not using the device.)

Somewhere on the circuit board, you may find a point, where power is available for those 20 seconds, to light the led.

Only if you are lucky will you be able to find that spot.

It may be a path to ground, or else a connection to +9 V. To find it, you will no doubt have to test the voltmeter on several spots.

You will need to solder a wire to that point, and then you will need to solder a second wire to a second spot which will be either +9V or ground (depending which arrangement gives you power).

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Or, there is a bare chance it will work for you to tap across the speaker leads.

The AC voltage applied may be at sufficient amplitude to light the led. This possibility is interesting because the led will flash brighter when sound is louder.

Also look to see if the speaker has a DC blocking capacitor inline. You would hook the led across both the speaker and capacitor.

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If you cannot get sufficient voltage at the speaker, then you can add a transistor in such a way as to drive the led, at varying brightness according to loudness.

 

[HvEdtg83]

BradtheRad,
I was beginning to think twice about adding the electronic elements due to time constraints, but your note about connecting the LED to the leads of the speaker fascinated me and ended up working extremely well.
Many thanks for the inspiration



The look on his face says it all.

 

[BradtheRad]

Really, really great.

Wow, that cake is almost as big as he is!

I'm glad it worked for you.

Your boy may be inspired to take up electronics and build a real R2D2 someday.