The main PCB for the charger is a single sided, 1.6mm tick printed circuit board. The DC/DC converter is now integrated within the charger in order to allow the charge of high number cell packs. The people that charges only few batteries (12Vdc supplies sufficient) can not mount the components for the DC/DC converter saving the money of this part. The DC/DC converter part is a generic step-up converter, capable to deliver 7.5A and an output voltage of 24Vdc, starting from a 12Vdc supply. The main parts are the following:
- PWM controller UC3843 very cheap and easy to find
- Power inductor from Bourns, type 2306RC (27uH, 15A), Farnell 1167731
- The power diode is a schottky type,and a N-type mosfet can be generic: all the two components are in case TO-220
Universal Charger: [Link]
For this project you will need a disposable camera. Why a disposable camera ? Because the flash circuit inside the camera contains a hi-voltage oscillator and transformer that outputs about 300 Volts AC & DC. When opening the camera to get to the flash circuit you should be extremely careful so you don’t get electrocuted by the high voltage’s inside the capacitor. First thing you need to do is to discharge the capacitor so its more safer to work with. Then with a small modification into the existing circuit you’re ready to power the 4 watt fluorescent lamp
4 Watt fluorescent lamp powered by a 1.5 volt battery: [Link]
T1 steps down AC voltage from 115VAC (or 220VAC) to about 8VAC and is then rectified via bridge rectifier BR1 to about 11.52Vdc. C1 filters off the AC ripple. If you find the circuit output too noisy add another electrolytic capacitor over the output terminals. Value can be between 10 and 100uF/25V. The output voltage is variable with the 10K-potentiometer while keeping the current constant.
T1 = 115/8 VAC transformer. Center Tap not needed.
Q1 = 2N1613, NTE128, or substitute. (TO-39 case) On coolrib!
BR1 = 40V, 4A. (Check max current of your mini-drill and add 2A)
R1 = 470 ohm, 5%
R2 = 1K, 5%
P1 = Potentiometer, 10K
C1 = 1000uF, 25V, electrolytic
C2 = 0.1uF (100nF), ceramic
Variable Power Supply for mini drill: [Link]