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Modifing Variable speed rouder control, Help?

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Forum topic by Hami posted 06-27-2013 08:20 AM 659 views 0 times favorited 6 replies Add to Favorites Watch
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Hami

5 posts in 1261 days


06-27-2013 08:20 AM

Topic tags/keywords: question router speed control electronic geek help

Hi,

I’m trying to make/modify my router from internal speed control to external? The manufacture has parts to do this, but i don’t want a knob. I want more of steps, I what to replace the knob with a resistors and switches. Yes it sound like going back into the dark ages from full variable.

It was to be a simple task, get the pot and replace it with resistors and switches, Here is the problem, the Pot has three wires to it and as you turn the Pot c to cc, the resistance climes on one set, drops on the other, and dose not change on the other.

Can some one enlighten me on what is going on here?

Electronic Geeks Welcome!

Hami


6 replies so far

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RonInOhio

720 posts in 2331 days


#1 posted 06-27-2013 10:13 AM

I don’t believe three terminal potentiometers are often used to control more than a watt or so. They are usually used in low line level voltages, to indirectly control output. Check your voltage and current rating of the pot.

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Hami

5 posts in 1261 days


#2 posted 06-27-2013 11:26 AM

I agree, I believe it is controlling one or two Triacs.

There is no part number on the pot, only the manufacture logo and its rating, only resistance.

View crank49's profile

crank49

3981 posts in 2437 days


#3 posted 06-27-2013 01:46 PM

The “pot” has a resistor (carbon layer on bakelite or fiberglass base) connected between wire #1 and wire #2.
The shaft turns a wiper that is attached to wire #3 and contacts the surface of the carbon strip as it rotates.

To replace the function of this you measure the ohms between #1 and #2. Guessing it’s about 10k ohms.
Each switch position will have two resistors that must total the ohms measured between #1 & #2. Say a 2k ohm and an 8k ohms attached to wires #1 & #2 respectively. Wire #3 goes to the switch and between the resistors. This switch would be about 20% of max speed.

Repeat this process for each switch position.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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Hami

5 posts in 1261 days


#4 posted 06-27-2013 01:54 PM

But, what is the other end doing, is it using both wires?

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crank49

3981 posts in 2437 days


#5 posted 06-27-2013 04:16 PM

This is one way to do this. Certainly not the only way.
Depends on what components I find in my parts bin.
This uses a 2 gang 3 position switch.

Some circuits don’t use all three wires on a pot.
Much simpler since you only need a single gang switch and 3 resistors.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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Hami

5 posts in 1261 days


#6 posted 06-27-2013 05:30 PM

They have all three wires included in the harness, and in the cable back to the router

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