DC control

Efried said:
Hello,
 
I wonder if you have experience controlling DC-voltage for fans, brushed motors and the like?
Here is one solution, I have to clarify if this is adaptable for my purpose switching supply voltage to fans from 12V to 9V...
Click to expand...
 
I have a number of fans being controlled from various WC8 boards.
If you don't need precision, infinitely-variable speed, just on/slow/fast for example, most of these computer case fans etc will operate very nicely on full volts and somewhat less. Eg, a 12V case fan will usually work adequately on 5V for an almost silent, low-speed fan.
 
Digital outputs from the WC board can easily change the drive to a linear regulator, or (as I have done before) simply switch on or off one of two or three BC337 transistors, each wired as open-collector. High speed provides full volts. Medium speed has a 3V3 zener, low speed has a 5V6 zener in series with the collector.
 
This way, you can turn on no outputs (slow), or one of the voltage-select outputs for the speed you need. Cheap, effective, simple.
 
rossw said:
I have a number of fans being controlled from various WC8 boards.
If you don't need precision, infinitely-variable speed, just on/slow/fast for example, most of these computer case fans etc will operate very nicely on full volts and somewhat less. Eg, a 12V case fan will usually work adequately on 5V for an almost silent, low-speed fan.
 
Digital outputs from the WC board can easily change the drive to a linear regulator, or (as I have done before) simply switch on or off one of two or three BC337 transistors, each wired as open-collector. High speed provides full volts. Medium speed has a 3V3 zener, low speed has a 5V6 zener in series with the collector.
 
This way, you can turn on no outputs (slow), or one of the voltage-select outputs for the speed you need. Cheap, effective, simple.
Click to expand...
 
thanks, are the transistors and diodes introducing losses?
I had bought a digital resistor and hoped to exchange an manual potentiometer of a motor controller, but the switched voltages suffice and would reduce my work.
best
 
Efried said:
thanks, are the transistors and diodes introducing losses?
I had bought a digital resistor and hoped to exchange an manual potentiometer of a motor controller, but the switched voltages suffice and would reduce my work.
best
Click to expand...
 
Well, anything introduces losses.
If it's a small fan like a PC Case fan that only draws 200mA at full power, then the losses are fairly small.
(It will draw less current at lower volts. Some very rough figures: adding a 5.6V zener will reduce the fans supply from 12V to about 6V, its current will probably be closer to 120mA, you will be wasting around 650 milliwatts. (Obviously size the zener accordingly))
 
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