Hello,
I have a 24v 1.6A DC Brushless fan but only a 12v power supply. I was wondering if I could use the tach pulse from the fan to run a pumped DC voltage doubler similar to the clock generated from a 555 timer: http://www.electroschematics.com/648/555-voltage-doubler/. The added benifit is that the voltage will ramp up from 12v to 24v as the fan spins up.
The first problem is that because I only have a 5v DC square wave from the tach, I have to pull down the PNP base with a resistor. The second issue is that all of the voltage doubler examples I can find use less than a 12v supply so my circuit has to be protected with more resistance. I can't seem to get it working and I was wondering if someone could recommend the proper wiring and resistor values from the tach signal to the shared base terminal and from the NPN base to ground.
All I have left in my tickle trunk that can handle the current is a TIP31B (NPN-tran,5v base) and a BUZ71 (N-MOS, 7v gate) which seem to work alright together. Let me know if I need to get some more suitable transistors.
Thanks in advance
I have a 24v 1.6A DC Brushless fan but only a 12v power supply. I was wondering if I could use the tach pulse from the fan to run a pumped DC voltage doubler similar to the clock generated from a 555 timer: http://www.electroschematics.com/648/555-voltage-doubler/. The added benifit is that the voltage will ramp up from 12v to 24v as the fan spins up.
The first problem is that because I only have a 5v DC square wave from the tach, I have to pull down the PNP base with a resistor. The second issue is that all of the voltage doubler examples I can find use less than a 12v supply so my circuit has to be protected with more resistance. I can't seem to get it working and I was wondering if someone could recommend the proper wiring and resistor values from the tach signal to the shared base terminal and from the NPN base to ground.
All I have left in my tickle trunk that can handle the current is a TIP31B (NPN-tran,5v base) and a BUZ71 (N-MOS, 7v gate) which seem to work alright together. Let me know if I need to get some more suitable transistors.
Thanks in advance