| Author | Message | ||
| Jim and Myrna Lawrence (Daffycanuck)
Rating: N/A |
I use a Haden 12v Radiator Cooling fan as a fan on my interior, down the road, heater. It blows a lot of air and I'd like to add a low speed circuit to the fan motor. Can someone tell me what size resister I need to incorporate to add the low speed. Thanks | ||
| TWO DOGS Rating: N/A |
GO TO A SHOP THAT BUILDS GENERATORS & ALTERNATERS | ||
| TWO DOGS Rating: N/A |
or...better....TAKE it to that shop | ||
| John that newguy Rating: N/A |
In the "for what it's worth" department: _______________________________________ DC Motor Speed Controller Vary the speed of DC motors the very best way with this kit. Gear boxes can be costly and series resistors may cause stalling. This circuit delivers the voltage to the motor with pulses and the speed is controlled via pulse width modulation (PWM). The speed control is a potentiometer, for DC motors up to 100 Volts at a maximum of five amps. #80-670 DC Motor Speed Controller kit http://www.philmore-datak.com/Page209.htm _______________________________________ I think I'd just run over to the local RV supply shop and buy a dc control (rheostat) that's on the higher priced exhaust fans. (radio shack's got "stuff" too!) | ||
| Jim and Myrna Lawrence (Daffycanuck)
Rating: N/A |
Thanks.....John the NewGuy has given me the answer.....one I should have seen as I have two of those fans..... | ||
| John tng Rating: N/A |
If you're going to use a rheostat on an automotive radiator type fan, be careful! Depending on the draw of that motor, a rheostat can get damned hot. The resistor is taking the power instead of the fan.. It can get HOT enough to cause combustion. | ||
| BrianMCI Rating: N/A |
You will just need to size the rheostat to handle the load... There used to be aftermarket replacement heater blower motor rheostats with a ceramic base... That might work if they still make them. Something to think about...GM used a group of resistors for their blower motors in the 90's and stuck them into the blower's air stream... Mounting the rheostat attached to a heatsink is another thought. Brian | ||
| Sojourner
Rating: N/A |
You can use DC Motor Speed Controller but limit to 5 amps. Or you can use several diodes in series. Each silicon diode is .7 (point 7) volts drop. Example 6 diode = 4.2 volts drop. Whatever current (amp) draw of motor w/fan at full voltage will be half current at half voltage. Radio Shack; http://www.radioshack.com/search.asp?find=diode&hp=search&SRC=1 ??pc..3 amps @ 50 v # 276-1661 1pc…30 surge-amps @ 400 v 1N4004 # 276-1103 1pc…1000mfd @ 24 or higher volts capacitor http://www.allelectronics.com/cgi-bin/category.cgi?category=205&item=P600M&type=store 2 = 6amp @ 1000volts for $1 at walk-in (Van Nuys, CA) or plus shipping $6. About Diode; http://www.kilowattclassroom.com/Archive/DiodeRec.pdf You can parallel diode to double ampere rating. Such as 2 x 3 amp diodes = 6 amps in parallel. And a 1N4004 diode snubs out potential spikes from the motor, and the 1000uF capacitor across the motor eliminates motor brush noise from the DC wiring. Caution. Diode will short out if over rated voltage feed back such as spikes. So purchase diodes at least or higher ampere & double the voltage rating for your need. Here a schematic of  jpg format Hope download work? My first time. For what it's worth. Sojourn for Christ, Jerry | ||
| Sojourner
Rating: N/A |
Resize drawing of Two Speed DC Fan  Sorry for repeat. Sojourn for Christ, Jerry | ||
| Sojourner
Rating: N/A |
Resize drawing of Two Speed DC Fan Sorry for repeat. Sojourn for Christ, Jerry | ||
| James Stacy (Jimstacy)
Rating: N/A |
When you said you have two fans it wasn't clear if you were running both of them, if so just run them in series for low speed, parallel for high speed. GM does this for the defroster blowers. No heat, no wasted electricity. You will need a double pole, double throw, center off switch. FWIW Jim Stacy | ||
| Stephen Fessenden (Sffess)
Rating: N/A |
If you decide to use dropping resistors put them in the air stream for better cooling. |