Fooling around w/one of Colin's circuits (3V-9V converter)

[Mosaic]

You can replace a 9v battery with this circuit.
The output is about 10.4v on no load and 9.6v @30mA output.
The advantage is the voltage stays over 9v for the life of the cells.
A normal 9v battery drops to 7v very quickly.
The output voltage is set to 9-10v by the 6k8 and 390R resistors. The 470R gives the circuit an idling current of about 20mA. The spikes are about 75mV.
**broken link removed**

Colin.....

Would 4.5V from 1.5V be possible?

I have an old HP28s calc that wants 3 Ncells for 4.5V. I'd much rather run it it with 1 AAA 1.5V alkaline due to the cost & availability of N cells were I live. Radio Shack wants 6 USD for a pair!

I can get 6 AAA (equiv.) from one 9 V alkaline for about 3 USD.... 0.50 USD per AAA/alkaline or a buck per pair ...a 3 x savings.

Using 1 AAA would give me the remaining batt space (about 125% AAA volume) to build the circuit. The batt. compartment cylinders are 12mm wide x 60mm and 12mm by 30mm holding the 3, 12 x 30mm N cells. . So the AAA will occupy 44mm of the 60mm tube and I still have another 30mm tube free.

Can it be done?

 

[audioguru]

A 9V battery has six AAAA cells inside, not AAA cells. A skinny AAAA alkaline cell has a capacity of only 460mAh, an AAA cell is 1000mAh and an AA cell is 2500mAh. So an AAAA cell will not last long.

 

[colin55]

For 5v, the voltage divider should be 3k9 and 560R