Mr. Mik
1 kW
- Joined
- Sep 3, 2008
- Messages
- 390
The discussion about this topic started a bit "off topic" in this thread:
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=8722#p133439
SInce then I have bought and tested one of these Potentiometers:
http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
" 5 Ohm, 15W Wirewound "
It produces smoke....but apparently not the magic kind of smoke, because it all still works.
The problem seems to be that the motors have a controller built in, and this controller stops the motor if the supply voltage drops too much. That is probably also the reason that the impellers often start running with a delay of a few seconds between them. One starts first, draws too much current and drops the voltage too low for the other. The, when it is fast enough and the current draw drops to about 2 to 2.5A, the other impeller motors starts to chime in.
I connected the 5 Ohm Pot in line with the negative cable returning from the impeller motors.
Starting with the pot turned to 0 Ohm, it runs fine. When the pot is gradually turned up, then the fans slow down. At some point around 0.5 to 1 Ohm the fans turn off, and then one starts running again, but stops when the other starts about 2s later; they alternate running for a few sec at a certain Pot setting.
Oh, and then there is that smoke coming out of the pot, the smelly kind. It did not start at first when I turned the resistance up, but once it had started it came back quickly each time the pot was turned up from zero and the impeller motors slowed down.
So far, it seems that only a small reduction in impeller speed and noise could be achieved with resistors, but this would cause a lot of heat and still use a similar amount of power. I guess that about 0.5 Ohm might work, maybe 4 x 2 Ohm (10W) in parallel.
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=8722#p133439
SInce then I have bought and tested one of these Potentiometers:
http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD
" 5 Ohm, 15W Wirewound "
It produces smoke....but apparently not the magic kind of smoke, because it all still works.
The problem seems to be that the motors have a controller built in, and this controller stops the motor if the supply voltage drops too much. That is probably also the reason that the impellers often start running with a delay of a few seconds between them. One starts first, draws too much current and drops the voltage too low for the other. The, when it is fast enough and the current draw drops to about 2 to 2.5A, the other impeller motors starts to chime in.
I connected the 5 Ohm Pot in line with the negative cable returning from the impeller motors.
Starting with the pot turned to 0 Ohm, it runs fine. When the pot is gradually turned up, then the fans slow down. At some point around 0.5 to 1 Ohm the fans turn off, and then one starts running again, but stops when the other starts about 2s later; they alternate running for a few sec at a certain Pot setting.
Oh, and then there is that smoke coming out of the pot, the smelly kind. It did not start at first when I turned the resistance up, but once it had started it came back quickly each time the pot was turned up from zero and the impeller motors slowed down.
So far, it seems that only a small reduction in impeller speed and noise could be achieved with resistors, but this would cause a lot of heat and still use a similar amount of power. I guess that about 0.5 Ohm might work, maybe 4 x 2 Ohm (10W) in parallel.
