# Router Speed switch (after market)



## builtinabarn (Feb 17, 2009)

I have an older (about 8 years old) Porter cable 3 1/4 hp Router with what I believe to be a soft start. This model does not have the variable speed switch. All the after market speed switches mentioned that they do not work with routers with "soft start". Can anyone tell me why this is? Or does any one know of a way around this. I have some raised panel doors to make and I'm using a 3 1/4" bit in my router and need to slow down the speed.


----------



## EEngineer (Jul 4, 2008)

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.


----------



## builtinabarn (Feb 17, 2009)

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


----------



## EEngineer (Jul 4, 2008)

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.


----------



## builtinabarn (Feb 17, 2009)

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


----------



## alanealane (Oct 1, 2007)

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!!


----------



## builtinabarn (Feb 17, 2009)

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


----------



## builtinabarn (Feb 17, 2009)

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


----------



## EEngineer (Jul 4, 2008)

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?


----------



## Karson (May 9, 2006)

Great tool modification.


----------



## khill951 (Jun 16, 2009)

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.


----------



## builtinabarn (Feb 17, 2009)

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.


----------



## GaryCN (Aug 18, 2007)

Has anyone tried this controller MLCS 9410 20-Amp Heavy Duty Router Speed Control 9410 20-Amp Heavy Duty Router Speed Control about $15 less than the Rockler


----------



## decoustudio (May 4, 2006)

Another reason to love lumberjocks. I'm an ME and never get tired of hearing EE's talk shop….ok, ok, that isn't true, because I don't hardly understand anything they say. However, it just amazes me what they can do, and what I can do with their designed tools and equipment. Thank God for EE's, at least some of them..

Thanks EEngineer for your thoughts on this.

Mark


----------



## NBeener (Sep 16, 2009)

As a guy who was a EE major (technically, pre-law and EE, double major), but never used it … I like hearing EEs talk, AND …. watching what you *ME's* can DO 

That WAS a cool thread, though: reminded me of MASH, when they had to talk somebody through a surgery-over the radio-when the person doing the surgery … wasn't a surgeon !


----------



## builditrite (Feb 18, 2015)

Old post, but I thought I would make clear how I bypased the soft start. Khill951 has it right. My power cord had the white lead going directly to one of the brushes. That same connection had a purple( also neutral) wire going to the control board, i suppose to provide the board with a reference. I clipped that wire at the source, as it was not needed The black lead from the power cord went to the switch, the other side of the switch (white) went to the conrtrol board. From the control board it came out as a red lead going to the other brush. So, clip out the board, disregard and cap the purple (duplicate) neutral, then tie the white (switched leg) from the switch to the red (leading to the other brush) and your're done. Alternatively, leave the board in, clip the purple and solder a 14 Ga wire between the solder leads from the white to the red wire. If she don't smoke, yer done.


----------

