| Forum Home | ||||
| Press F1 | ||||
| Thread ID: 44250 | 2004-04-13 03:33:00 | Potentiometer mods! (i.e. control your fans) | hamstar (4) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 228943 | 2004-04-13 03:33:00 | This is one for the buzzheads in the house... (hehehe) Can I use any old potentiometer between my 12v/ground and my 80mm/120mm fan? Or does resistance come into it in a big way. Ignorance is bliss atm, but I thought that I just got a pot and whacked it between a power source and wire and it'd work fine.... If I need a certain amount of resistance does that mean i have to have a huge pot? |
hamstar (4) | ||
| 228944 | 2004-04-13 03:45:00 | I have tried controlling small electric motors with potentiometers, very unsuccessfully. I have a feeling that you'd need a very very low resistance pot, or some kind of more complicated circuit to make it work. | somebody (208) | ||
| 228945 | 2004-04-13 04:00:00 | "any old pot" is unlikely to work. Frying pans aren't very good for this application, either. The size of a pot (or rheostat) depends on its power rating. How about a few rough numbers ... First look at the name plate of the fan, which should tell you the rated current. If it's 80 mA, the "resistance" of the fan will be given by R=V/I ... 12/80x10^-3, ---> 150 ohms. This amounts to 9.6W. You're going to find pots with a decent power capability fairly hard to get. The motor is most likely a "brushless" one (the DC is converted to 3 phase AC) so there will be a limit to the range of voltages it will work on. If you used a 150 ohm power resistor, this would give approximately half voltage across the fan, and the power used would be 1/4 of that ... 2.4W to the motor and the resistor would dissipate 2.4W. A 150 ohm, 5W resistor would run fairly warm. I'd go for a 10W. Lower value resistors would probably be OK at 5W rating. DSE and Jaycar have these power resistors. You will need to experiment with various values (100, 50 ...) You might find a 3 position toggle switch to select between "no resistor" and a couple of different resistors. |
Graham L (2) | ||
| 228946 | 2004-04-13 06:18:00 | I'm currently using one of the DSE voltage regulator kits to control my fans. It had no trouble powering 5 fans (with a heatsink on the IC), but normally only have 3 connected. The only problem is you loose a few volts so the maximum output is around 10.5 volts, which is not a problem in my case since I run them at ~3 volts. Cost: $15 for the DSE kit. $5 for a plastic case. ~$5 for extras: Power connectors, a pot to control the voltage, etc. |
bmason (508) | ||
| 228947 | 2004-04-13 08:30:00 | > Can I use any old potentiometer between my 12v/ground > and my 80mm/120mm fan? I hear running Windows XP instead of Win2K would be better for what you want. /end sarcasm ;) Lo. |
Lohsing (219) | ||
| 1 | |||||