D
**DONOTDELETE**
Guest
Hi Guys!
I took 3 days of my holiday to deal with the problem that there is no easy step up converter to power a white LED on 1 AA cell.
Either you can build the SatCure circuit, which makes a lot of trouble winding the coil, or you can use a ready to go IC which can only be bought from the manufacturer and is SMD (hard to solder). Getting the coils for these circuits is hard also, because RadioShack and similiar shops dont have them.
Now I made a circuit which works only with resistors, capacitors, and easy-toget-and-cheap Transistors (BC547C and BC557C, both at about 10 cents apiece). The disadvantage of this circuit is that is relatively large (16 transistors!) and can power only one LED at 20mA, pulling 170mA out of the battery (not very good efficiency).
How it works:
1. An instable multivibrator generates a rectangular signal of about 10 kHz.
2. This signal drives a H-bridge of 4 Transistors to lower impedance.
3. This signal is sent through a voltage multiplying cascade of diodes and capacitors.
4. To minimize voltage drop across the diodes in the cascade, they are replaced by transistors (so the 0.6V voltage drop across the diodes are reduced to about 0.1 to 0.2 V).
Some technicals:
I(LED)=20mA at Uin=1.500V
I(LED)=3mA at Uin=1.000V
I(batt)=170mA at Uin=1.500V
I(batt)=39mA at Uin=1.000V
The input voltage should not exceed 1.6V, because this will make the output voltage drop and the circuit will draw large currents from the battery.
If you have any questions, suggestions or improvements, please tell me.
And if you want a large image:
http://briefcase.yahoo.com/stepupcircuit
Bye!
I took 3 days of my holiday to deal with the problem that there is no easy step up converter to power a white LED on 1 AA cell.
Either you can build the SatCure circuit, which makes a lot of trouble winding the coil, or you can use a ready to go IC which can only be bought from the manufacturer and is SMD (hard to solder). Getting the coils for these circuits is hard also, because RadioShack and similiar shops dont have them.
Now I made a circuit which works only with resistors, capacitors, and easy-toget-and-cheap Transistors (BC547C and BC557C, both at about 10 cents apiece). The disadvantage of this circuit is that is relatively large (16 transistors!) and can power only one LED at 20mA, pulling 170mA out of the battery (not very good efficiency).
How it works:
1. An instable multivibrator generates a rectangular signal of about 10 kHz.
2. This signal drives a H-bridge of 4 Transistors to lower impedance.
3. This signal is sent through a voltage multiplying cascade of diodes and capacitors.
4. To minimize voltage drop across the diodes in the cascade, they are replaced by transistors (so the 0.6V voltage drop across the diodes are reduced to about 0.1 to 0.2 V).
Some technicals:
I(LED)=20mA at Uin=1.500V
I(LED)=3mA at Uin=1.000V
I(batt)=170mA at Uin=1.500V
I(batt)=39mA at Uin=1.000V
The input voltage should not exceed 1.6V, because this will make the output voltage drop and the circuit will draw large currents from the battery.
If you have any questions, suggestions or improvements, please tell me.
And if you want a large image:
http://briefcase.yahoo.com/stepupcircuit
Bye!