Howdy,


I am not anyway near to needing to think about the heater control (so I haven't done anything) . BUT, I may just buy one anyway just to experiment with it.

The Pulse Width Modulated speed control IS the most efficient way to control the speed of any DC motor and regardless of where you operate the motor, it will generate very little heat

 

I am useing my heater ..how the heck do you get the defroster working ?? an were do you get ..pulse mod-u-lated (?) controls..I thought it was normal to have that glow from the switch when you turned on the heater ..

 

If you have the box-type heater, the defrost is always on.

The switches with resistors in them sometimes also have a little bulb in them that is brightest when turned up high.

 

Cool, thanks for the info. I had hoped someone else had bit the bullet already and might save me the 'learnin the hard way' experience. I've googled up all I can stand and am the point that as soon as the DMV gets their poop in a group I will pull it out of the shop with a destination of my place finally... So I guess I'll be the lucky one who gets to try it (the PWM) first. I will definitely post back my finding.




The PWM was 1st mentioned above by rick, so I have to give him credit... from the application I would say you could probably find it at hobby train/ rc car type places... perhaps a well stocked electronics place (doubtful radio shack - something better equiped), and of course online what rick linked us:
MX033 - DC PWM Motor Speed Controller 15 Amp - Assembled & Tested


I am thinking I will go to radio shack and get one of their small project boxes (little black plastic box) to enclose all the back 90% in, and then it will be slightly less noticable behind the bracket. Pics, and all to follow... ordering now.

 

I wouldn't even try using PWM unless you have an alternator, or you'll have to include a pretty substantial power smoothing circuit. The voltage spikes a generator gives off would probably roast the electronics. Even with an alternator it wouldn't be a bad idea, car power systems aren't that "clean".

 

There ya go again settin me back another day Ross

I have converted to 12v, and have a junk yard pulled high output alternator (Ford 4g from a 2000+ F250 - none of the older 1 wire or simpler design alts were still salvagable looking or had reasonable miles).

I know my batt gives a nice clean 13.8v very steady with no fluxuation in the needle on an ANALOG multimeter (DMM's just don't give you the fine bounce and slow sweep diagnostics - lots of old telephone guys still carry analogs).

I'll check my alternator output with the multimeter across the rpm range before I click submit on my order now

(I have a dash volt meter that reads very consistent, but no idea what autometer did in the brains of that thing... will check with multimeter)

Not to argue or start something someone else will attack, but I thought auto power was always a lot cleaner than say home - no miles of transmission lines, no damage / weather variations, not competing with 200+ neighbors. Just you and what is under the hood, regulator right there at the source & distribution close to the accessories, even on the old 6v systems.... Did the old regulators just not clean it up that well? I suppose there was a lot of inductance issues (ever have a radio that didn't whine static and change pitch with the speed of the generator ha)

 

Auto electrical power systems can be pretty "spiky". Spikes are commonly generated by a starter or old type generator.



Just get a rather high value electrolytic capacitor and "place it across the main DC line. (mind the polarity..... PLUS/MINUS)



Your battery will absorb most of the spikes.

A BIG capacitor (200uf @ 100VDC or more) will pretty much get the rest.

Just rob one out of any old computer power supply etc....

 

Wouldn't an inductor be better at suppressing a spike? I would think the capacitor might just work on ripples.

For a completely different purpose, I got some absolutely huge electrolytics at an army surplus store -- 1.5" diameter, 4" long. They were dirt cheap.

 

A "network" approach might include an inductor but for a low voltage high current application, it would take a LOT of turns (with the resulting voltage drop across the inductor)

Another way might be to use a BIG zener diode (18V or so) or an MOV (Metal Oxide Varistor) like is used in "regular" "spike" protectors.

Big electrolytics are used in BIG (booming) audio amps . They supply the high peak currents that an audio amp needs (but the battery or alt cannot supply)

They also absorb BIG spikes!

 

The voltage that you see from either an alternator or generator is really an average of a series of sine waves. Occasionally, you can hear it in the radio. A capacitor can smooth that out to some degree. Here's a capacitor that is sold for aircraft applications...so it is spendy:ALTERNATOR FILTER from Aircraft Spruce


It'd be good to find the equivalent in an automotive grade....it'd be the same with a lower price tag.

Dan

 

EVERYTHING from Aircraft Spruce is "Spendy"!! Especially parts for a Stinson!

 

Haha....if you have a Stinson and a 50's ford truck, that just confirms that you don't mind going on a treasure hunt for NOS parts. God...do you have Eisemann magnetos on that Franklin??

For the alternator noise...I'm sure that Napa has some large capacitor for something that'd do the same thing at an automotive price. We just have to search a little!

Dan

 

Nah! It's got reg'lar Rabbit Bendix

 

Update:
Ross got me to pause and contemplate before I clicked 'confirm order'... I did a bit more shopping for a PWM after that.
I chose this one instead:
$10.39 Free Ship 12V-40V 10A PWM DC Motor Speed Controller w/ **** - Wholesale US$9.49

My fan runs about 90% of speed with a 6v 2a trickle charger, and does not overload the charger. (headlights by themselves will overload the charger putting it into fault mode)

Running the fan through a 4a ceramic 12v to 6v reducer (common LMCtruck voltage reducer) does not get the ceramic reducer hot at all. The fan has no markings on it, but I am gathering it must draw about 2-2.5a at wide open.

So all that said, I don't think I need a 30a or such big monster switch/pwm.. a 10a would be fine (and that link above was only $11 / free shipping... if I nuke it with a spike I won't cry like if I had nuked a $50 part).

I have a salvaged 220uf 200v 105degree capacitor that has no signs of leak. (yes chopped out of a computer power supply even)

Based on advice above, and some googling I am going to do the following (correct me now before I fry my new PWM like a n00b)

positive lead from fuse block
|
/ \
| cap +
| cap -
\ /
|
pwm + (v+ in)
pwm load out +
|
reducer 12v in
reducer 6v out
|
fan


pwm v- and pwm load out - all connect to ground
fan is grounded through frame

It hurt my head a bit to think you would connect the capacitor and bypass it both, but multiple electronics sites said that... if I got it wrong edumacate me now please.

Of course I'll do pix and 'how to' followup if anyone is interested.

 

That looks like a great deal!