Router Speed switch (after market)

OK, let’s give this a shot.

The way they do soft-start and speed control (note that a lot of the variable speed controls also do soft-start) is to insert a triac in series with the power to the router and switch the power ON for only a portion of the AC cycle. Since triacs continue conducting until current goes to 0, they watch for the zero-crossing of the AC signal, wait a little more, then turn on the triac and let it conduct until it crosses 0 again. For instance, if you wait for 90 degrees of the half-cycle (each 1/2 cycle = 180 degrees), then turn on triac and let it conduct the rest of the half-cycle, you get about 1/2 the power, 1/2 the speed on a universal motor (this only works for universal motors, do NOT try on an induction motor). Soft-start works the same way but gradually ramps up the effective voltage/current by truning the motor ON for progressivley larger amounts of the half-cycle until it finally is conducting for full half-cycles which gives full power and full speed.

Unfortunately, when you connect two of these controllers in series with each other, they confuse the hell out of each other. The first in the chain sees normal line voltage and zero-crossings as it should. The second in the chain doesn’t see normal line voltage. It only sees voltage when the first in the chain turns on. It sees this as the zero-crossing. Let’s say both are trying to deliver 1/2 voltage/current. The first in the chain sees zero-crossing, waits for 90 degrees and then turns on its triac. The second controller sees the first turn ON, counts this as a zero-crossing, waits for 90 degrees and then turns on its triac. Unfortunately, by the time it turns on, 180 degrees of cycle have gone by and the voltage/current is going through zero again. Net result is zero current/voltage through the motor.

The fix is fairly simple- disable the soft-start in your router. As I mentioned, lots of the variable speed units offer soft-start as well. If you can talk PC out of a wiring schematic for your router, it should be as simple as removing the soft-start circuit and wiring the router motor directly to the line. Then wire a variable speed controller in series with your modified router.

-- "Find out what you cannot do and then go do it!"

Wow, I had to read that 3 times but I think I get what your saying. There is a great site called “toolpartsdirect”.com and they have schematics on almost any power tool (power hand tool). I really appreciate your response. If I get the schematic and I don’t understand sometime, I’ll get with you again and maybe you can answer another question for me Thanks again

-- Built in a Barn Bob

Sorry if I lapsed into “techno-babble” – electronics is what I do for a living. This question comes up on forums quite a bit and I looked into it a few years ago to see what the issues are. Sure, if you get a schematic and/or assembly drawing, I’ll take a look.

-- "Find out what you cannot do and then go do it!"

I got the schematic on the router and disabled the soft start, actually I just took the whole mechanism out. Hooked it to the new router speed control and it works like a charm. Thanks again for your help

-- Built in a Barn Bob

Thanks for this topic Bob!! I posted a topic a long time ago asking if a big PC router for my router table would be a good choice since I want to use the external VS control as you do. Now I know I can pick one up and disable the SS circuit. And thanks to EEngineer for the explanation….it takes me back to electronics class. Don’t want to brag, but I knew what he was talking about on the first reading…but then again, I only took the class about 3 years ago in college.

Have fun!!

-- Lane Custom Guitars and Basses

If you want the schematic, go to toolpartsdirect.com. In the search box select PC and enter the model number and its all there. I don’t recommend turning on the router unless you have that variable speed control hook up. That router takes off like a rocket without the soft start module . Good Luck

-- Built in a Barn Bob

Also, I bought the New Rockler router speed switch, its rated at 20 amps instead of all the rest at 15 amps and has a little more of a newer circuit board (up graded) . rockler.com

-- Built in a Barn Bob

Glad it all worked out for ya! It all made sense to me but I never had a chance to test it. How is the new speed control? Do you find any use for it besides just slowing things down for the extra large bits?

-- "Find out what you cannot do and then go do it!"

Great tool modification.

-- What happens in the workshop stays in the workshop. No wait that doesn't sound right. Karson Southern Delaware karson_morrison@bigfoot.com †

I cracked open my PC 7519 3 1/4 HP router and removed the soft start circuit board. It only took about 10 minutes. Just remove the moter housing and the soft start circuit board is wired between the on/off switch and the motor assembly. Simply remove the wire attached to the on/off switch that is connected to the circuit board. It should have a quick disconnect on the on/off switch. Remove the wire that connects the circuit board to the motor. (cut the wire or remove wire nuts if you are lucky.) Remove the circuit board. Attach a new wire from the on/off switch to the motor assembly. Put the motor housing back on and now you can plug your router into a speed controller. I first read about this fix on another blog and have since converted two PC 7519 with no problems. According to some of the other bloggers, they have done this numberous times with no problems.

I dug into this a few months ago and it turned out to be pretty easy. I did more or less exactly as you stated above. Thanks for the comment. Im sure there will be alot of others in the future that can read these posts and see how simple it was.

-- Built in a Barn Bob