Pimp my toy

The other day my 2-year old got a brand new firemen car that only played a sound or two and nothing more. The toy was quite dull but my kind was all over it because he loves everything with a siren.

I thought to my self. This ride need to be pimped. I said "Son I'm going to put an emergency light on that truck". He kept on going "Dadd...put...light...truck". Man was I under pressure.
So I did. I started to look at the car here:

Original toy

This is a 2xAA battery powered toy. So 3V doensn't allow me to use a popular 555 IC. To do a low voltage blinking led I needed and alternative circuit. So I remembered a simple oscillator circuit that is even easier to make. It' an astable multivabrator circuit made with 2 NPN transistors.

The circuit is similar to the one in this link.
Since this is such a low voltage application I replaced one of the collectors resistences by the LED directly.
This made the LED glow nicelly. I also changed some of the components values because of the LED blinking rate. The polarizing resistors were 47Kohm and the capacitors were 10uF. The transistors I used were a couple of BC549B I had laying around.

I took some prototyping pref-pcb and soldered the compontens. Don't mind the tallness of the components. I made this so I can (who knows) reuse them.



The astable multivibrator circuit


Looking at the toy there is a 2PDT switch that turns the toy on. The switch has 3 poositions OFF-DEMO-ON. So I will power the "blinker" in that switch for the ON position.



Identifying the ground and power spots



All soldered in place

 Then I took my dremel tool and drilled the roof of the toy bellow the light cover and glued it all in place with a hot glue gun.



Drilled roof top




Glued LED

 And here it is a PIMPED TOY CAR. The firemen truck now has a blinking light. I hope my son likes his "new" toy. ;-P

Toy with the added blinking emergency light