chconnor

Hi there -

So, like any red-blooded 21st century consumers, we have a blender. Cheap, brand X, but feisty, works great. Unfortunately, it's of the variety that is either off or 100% on, no intermediate speed settings.

I'd love to modify it to have the power/speed be controlled by a dial.

Can I just wire a pot into the hot leg of the mains power that varies the flow of current to the blender?

I haven't investigated further, because I thought perhaps there is something about the nature of the motor that would mean this isn't a good idea. Motors are somewhat mysterious to me :-) and something tells me that if it wasn't designed to run at a low RPM then doing so may not be wise.

I'd be satisfied if I could just use the knob to "slow start" the blender; that is, turn it gradually on and gradually off (say, over a few seconds) but only sustain the running at the top speed.

Thanks for any thoughts!
-Casey

chconnor

Ah, I now see this post:

http://www.electro-tech-online.com/e...r-circuit.html

...so maybe I need to investigate the motor more before asking this question... I'll try to do so and post again... And sounds like the simple pot isn't going to be a good/cheap/easy option...

-Casey

Hero999

What about using a simple lamp dimmer switch which can be purchased from a hardware store?

Just make sure it has a high enough power rating to control the motor.

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things

Don't use a pot, they are not meant to handle large currents a motor draws, and will most likely blow up. Use a lamp dimmer if you want a easy soloution.

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chconnor

Sounds great, I'm all over the (appropriately-rated) lamp dimmer. :-) So the motor won't be affected negatively by doing this, then? Not sure why I thought that...

And if I wanted to be able to reverse the motor... if it's an AC motor, is that even possible? Maybe it would require some more in-depth rewiring...

And if it's DC then I could reverse the polarity with a double-throw switch, and that would take place post-transformer inside the blender?

Thanks again,
-Casey

dknguyen

Don't blenders use AC motors? If so, just reducing or chopping the voltage won't make them run slower...just with less torque (although if it was an induction motor and not a synchronous motor, which is more expensive and therefore probably not used in a blender anyways, it might run slower just due to increased load on the motor.)

Controlling AC motor speed control is not nearly as straightforward as DC motors.

chconnor

Ok, assuming an AC motor, if I wire in that dimmer and turn it barely on, the lower torque is going to effectively translate to lower RPM when the blender is turning through my smoothie... I guess that's the concern I sort of subconsciously had: that operating the blender slower than it's designed speed (due to insufficient torque to get it up to speed) might be stressing it?

Or is it just going to be virtually stopped until it reaches some critical voltage and then lurches into motion?

Thanks again,
-Casey

spitso

sounds like a lamp dimmer connected to the mains before the circuit, is the best option i belive. Im after a dimmer switch aswell (using for a jacobs ladder) so far the best/cheapest place i can find one is off ebay for around $15. Pretty expensive units in generall.

3v0

Go down to the local thrift shop. The place that old appliances go to when their elderly owners depart this world. There is a good chance you can get a nice multi speed blender for about the cost of the a lamp dimmer.

The you can spend your time on something interesting like a remote control for the family dog

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chconnor

Well, got the dimmer, it works great. :-)

Am I crazy for wondering if the motor will be stressed or otherwise negatively impacted by running at lower voltages? Did I make that up?

Also, the dimmer seems to max out at 108 V, where our house mains are around 125 V, but the blender seems to run at about it's max anyway... Is that normal for dimmers?

Thanks!
-c

spitso

Glad it worked out for you. Where abouts did you purchase thi dimmer switch from and how much for? Im needing one for a jacobs ladder im building.

chconnor

Local hardware store... about $25. It is a self-contained box with a plug and a jack, not for use in a wall, etc. Which suits me fine.

RODALCO

Most blenders have an AC series wound motor, with commutator which works fine on a dimmer.

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chconnor

Great, so I will run it at low speeds with no fear. Assuming my AC motor is normal, and it's a pretty run of the mill blender.

Strange that the dimmer only goes to 108 volts, though. I guess it'll just have a bit less power (which is probably a good thing with this monster blender.)

I wonder still if there's a rating concern... the dimmer is rated at 1.2 Amps...

Thanks,
-c

mramos1

You can go to harborfreight.com and variable router and it will yield a variable speed knob for a router. Sure that pulls about what a blender would. I see them for $9.95 on sale. They are located all over the US.

http://www.harborfreight.com/cpi/cta...emnumber=43060