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Friday, 25 January 2013

9v Fast(ish) Battery Charger Stripboard Veroboard Layout


most of the chargers I own don't work fast enough - they take in the order of 14 hours so I thought "why not make one" since I have about 30 things with chargeable 9 volt batteries in them it would be nice to make a few of these. Anyway I wanted to make one that automatically cut off but it got a bit messy so I figured I would just drop the amount of current going into the battery so I could just leave it going for a few hours.

to work out charge time: hours = mAh / mA
example case: a 9v battery I have is rated at 150mAh
150 \ 50 = 3
therefore 3 hours

the LED illuminates when the battery is connected

the Transistor (BD135) needs to be heatsinked but the LM317 doesn't so if you're using a metal case you could just screw the transistor to the case and use that as the heatsink




Saturday, 19 January 2013

Floating Power Supply For DVM Panel Meters Stripboard Veroboard Layout


this was another one done out of necessity really.
I needed to power a panel meter from the same supply as I was measuring.
I actually didn't have the meter to test it with however it powered a cheap Digital Multimeter which I imagine takes up more current than a panel meter.
I also tried to make it small enough to be glued onto the back of the panel meter. 




Thursday, 10 January 2013

LED Crossfader Stripboard Veroboard Layout

This was a request I got via email, they wanted the LEDs to fade in and out to mimic some aircraft lights rather than just turn on and off so I came up with this little circuit. he also wanted it to run from 12 volts - so it does.
I was going to use an op-amp at first but I thought a 555 would yield a more consistent result