PWM Motor Speed Controller Regulator

[David Tilston]

The specs from the ad state 5% to 100%. It never shuts off. I plan to put it after the power switch on the fan itself.

[Joe Romas]

I tried a PWM on my fantastic fan and where the three speed switch is I mounted a variable resistor that also had a off switch, like a radio volume switch that's also the on and off switch. Kind of like this one but a little stouter I think.
10K-Ohm Audio Control Potentiometer with SPST Switch : Potentiometers | RadioShack.com

[Night Sailor]

My only issue so far is I switched the fan direction from in to out when on full speed and popped a fuse. I think was a 7.5 amp fuse. All I had was a 15 amp glass fuse to replace it. I rarely run it on high. I should take notes in this stuff.

[David Tilston]

Originally Posted by Joe Romas

I tried a PWM on my fantastic fan and where the three speed switch is I mounted a variable resistor that also had a off switch, like a radio volume switch that's also the on and off switch. Kind of like this one but a little stouter I think.
10K-Ohm Audio Control Potentiometer with SPST Switch : Potentiometers | RadioShack.com

Joe, that potentiometer is not rated to 10W. Odds are it is a 1/4W.

As discussed in the eariler part of this thread, the power on the resistor can reach 9W. This is enough to melt a 1/4W pot.

[David Tilston]

Originally Posted by Night Sailor

My only issue so far is I switched the fan direction from in to out when on full speed and popped a fuse. I think was a 7.5 amp fuse. All I had was a 15 amp glass fuse to replace it. I rarely run it on high. I should take notes in this stuff.

I have done that with a Fantastic fan repeatedly, (by accident). No fuse blew. I wonder if the PWM caused the current spike?

[John Linck]

David,

I would like to reduce the motor speed on my Suburban furnace. Do you think a PWM would be worth experimenting with? I want to achieve about a 10% reduction, but still enough to close the sail switch? From previous discussions the furnace seems to run fine and much quieter at 12 or even 11 volts. Am I crazy?

Thanks, john

[David Tilston]

Not crazy John. As long as the sail switch closes, I can't see a problem with what you are proposing. But I am no expert on your furnace. These PWM's will probably provide too much adjustment for your purposes.

[Night Sailor]

Originally Posted by David Tilston

I have done that with a Fantastic fan repeatedly, (by accident). No fuse blew. I wonder if the PWM caused the current spike?

It has to be a spike. I like to fuse things as low as possible. I would have thought that fuse would have held. I will probably swap it for a 10 Amp and see how that works.

[John Linck]

Originally Posted by David Tilston

Not crazy John. As long as the sail switch closes, I can't see a problem with what you are proposing. But I am no expert on your furnace. These PWM's will probably provide too much adjustment for your purposes.

That darn solar panel keeps my battery over 12.6 volts most of the time and the converter keeps the system voltage above 13.3 when I have shore power. So I expect the furnace blower is turning faster (noisier) than necessary, or is it already regulated? Previous discussions suggest not, and bringing the voltage down to 11 or 12 volts would quiet the blower. That would probably only use about 10% of the PWM's adjustment pot's range.

One downside is the heat exchanger may run a bit hotter, though surely Suburban must have planned for the low voltage of exhausted batteries. That's one reason for the sail switch, right? Might be interesting to measure furnace output temps as a function of battery voltage. Lower voltage = higher temps? Could always add outside temperature and altitude to the equation to make it really fun. Maybe when I retire.

Sounding crazy, even to me.
Might be easier to get some ear plugs. john ;-)

[Ak Ron]

Originally Posted by Ak Ron

I just installed my pwm in my fan today. For some reason, when I turn it all the way down it still wants to turn the fan slightly, drawing current. So I wired it in after the factory switch so I could turn it off. Another thing I noticed is that the potentiometer does not seem to be linear. most of the adjustment happens in the first 45 deg of rotation. I may have a defective unit if it won't turn off.

Thought I'd attach a few photos to show how I installed my pwm on the fan.
All the original components are still there in case of problems. I wired the module power + from an unused terminal on the existing switch. The module was hot-glued to the frame, as well as the wires at several points to keep them in place. The power out from the module goes to the reversing switch input terminals.

[Night Sailor]

Looks a lot like mine. Thanks for sharing. I should have taken pictures.

[David Tilston]

Yes, thank you!

[Bob Miller]

Originally Posted by John Linck

That darn solar panel keeps my battery over 12.6 volts most of the time and the converter keeps the system voltage above 13.3 when I have shore power. So I expect the furnace blower is turning faster (noisier) than necessary, or is it already regulated? Previous discussions suggest not, and bringing the voltage down to 11 or 12 volts would quiet the blower. That would probably only use about 10% of the PWM's adjustment pot's range.

One downside is the heat exchanger may run a bit hotter, though surely Suburban must have planned for the low voltage of exhausted batteries. That's one reason for the sail switch, right? Might be interesting to measure furnace output temps as a function of battery voltage. Lower voltage = higher temps? Could always add outside temperature and altitude to the equation to make it really fun. Maybe when I retire.

Sounding crazy, even to me.
Might be easier to get some ear plugs. john ;-)

If you slow the furnace fan down the sail switch won't stay open and the furnace will shut off, ending all of the noise.

[John Linck]

Originally Posted by David Tilston

I believe it was me that made the original suggestion:
http://www.fiberglassrv.com/forums/f...tml#post459872

I purchased the 10A vs the 3A version. It is bigger, but it has terminals for both the 12 DC in and the fan output. I plan to install it in the kitchen cupboard with the speed control knob sticking out.
6V 12 24V 10A Pulse Width Modulator PWM DC Motor Speed Control Switch Controller | eBay

Since it was only $1 more, I figured it was worth it.

The one that I suggested is also pictured below:
Adjustable Regulator Pulse Width PWM DC Motor Speed Controller Switch 6V 28V 3A | eBay

I think I would have been tempted to de-solder the connector and solder the wires directly.

I bought the 10 amp PWM (above) on ebay and installed it this morning, about one hour. I replaced the fantastic fan's on/off speed control switch with the Potentiometer wired to the PWM. Now the original reversing switch is also the on/off switch. Works great. Lots more speed adjustment range and much less amp draw at lower speeds and best of all its very quiet. I invested $5.00 for the PWM and about $50.00 in labor. ;-) I mounted the circuit board atop one of the motor struts where there is space and plenty of air flow. I have a cover over the vent lid so I don't expect it to get wet. Some day when I am retired I may spray the circuit board with some kinda water repellant sealer. The hardest part was working over my head the whole time. The PWM seems very well made. I hope it lasts forever. Stay tuned, I will report any issues.

Cheers, john

[Joe Romas]

Originally Posted by John Linck

David,

I would like to reduce the motor speed on my Suburban furnace. Do you think a PWM would be worth experimenting with? I want to achieve about a 10% reduction, but still enough to close the sail switch? From previous discussions the furnace seems to run fine and much quieter at 12 or even 11 volts. Am I crazy?

Thanks, john

John.
Check your email, I have done it.

[Joe Romas]

Originally Posted by David Tilston

Joe, that potentiometer is not rated to 10W. Odds are it is a 1/4W.

As discussed in the eariler part of this thread, the power on the resistor can reach 9W. This is enough to melt a 1/4W pot.

David.
On the PWM boards I have the pot is only used to control the modulator board and not handle the motor's current.

DC 12V 36V 5A 25kHz Motor Speed Control PWM Controller Control Board w Switch | eBay

However the contacts that switch it on and off are small.

[David Tilston]

Joe, I just re-read the post I replied to. I did not read it very carefully. I though you were just using a pot to control speed, when you clearly stated you used the PWM. Sorry for the confusion.