Speed control for the BT

[LCHIEN]

... Judging only from the sound of the router, I would say that the controller has some sort of circuitry in it to increase current when the router is under load. It sounds like the speed starts to fall off and then comes back.

...
Jim

The separate router control and router is a very dumb system. The router control has no idea of how fast the router is turning. or how much current it is drawing. It just adjusts the amount of voltage fed to the router.

The router motor speed is proportional to both the voltage and load.
When you set the speed control it sets the voltage. the router runs at one speed with no load and slows when you feed the wood into it. As the wood is removed, the load decreases and the motor speeds up, this is probably why you think its speed controlled. At that point your human nature is to react and feed it into the wood some more. The motor load controls the current, not the speed control.

A electronically contolled soft start router like the Bosch 1617evs and the PC 895VS and other similar routers use speed sensors that feed back to the controller to maintain speed. The reaction is almost instantaneous and you will never hear it slow down unless you approach motor stall conditions where the motor doesn't physically have the power to sustain the speed.

[JimD]

Loring,

I haven't researched this, perhaps you have, but I have both a variable speed router and the two fixed speed routers I have used with a speed controller. I can tell no real difference in how the variable speed router works versus the separate speed controller. I also question how a variable speed router senses speed. I do not think it has anything that measures the rpms. I think it is feedback circuitry to sense load. If that is correct, the same thing can be built into a separate controller. I am not saying that I know they are the same, just that they seem to be based upon use of both. I am having trouble understanding where there is a large difference as you suggest.

I would not suggest people who need a variable speed router buy a single speed plus a controller. I agree that would be a bit "dumb". I think the speed controller are an OK solution for someone who bought a router before variable speed was generally available (like me) or bought a single speed thinking that was all they needed and later want to spin large bits. For those situations, I do not think they are "dumb". Mine was pretty cheap, much cheaper than a new variable speed router, and works fine. I'm sure that the router designers do a better job with the dedicated speed controls built into the newer routers but I think the functional difference is less than you appear to believe. The biggest advantage I see to the built-in speed controller is the soft start feature that also seems to accompany this feature and the better idea what the different numbers on the dial mean. Those are valuable features which makes the variable speed router a better way to go IMHO for someone buying a new router.

Jim

[LCHIEN]

jim, i did not mean to imply dumb refering to the owner, just the speed controller. In order for the speed controller (which is a misnomer, it really controls conduction phase angle.) to apply strict control of speed, it must know what the speed is.

The motor speed is controlled by voltage and load. No necessarily an aboslutely linear relation ship and in any case depends upon the characteristic of the motor. A large motor would slow down less unde the same load as a smaller motor. So load alone is not an indicator of correct speed.

The speed controller is really just a glorified lamp dimmer. It sets the portion of the sine waveform in which it will conduct based upon the knob setting and because voltage is supplied only a fraction of the full time, the voltage is reduced.

The conduction angle control is done with a synchronized switch; either on or off so there's really no load sensing at all.

In order to strictly control constant speed, RPM feedback is required. There's only the power wires and no feedback signal. Even if there was a feedback signal there is no standard on the kind of sensor and signal.

Only in an all-in-one control and router can there be true constant speed control because then the manufacturer has access to the speed sensor and control of the signal characteristics. Also like you said a time/control of speed (e.g. soft start) and calibrated speed dial is possible.

Its not dumb to buy a separate dumb controller when you already havea single speed router, altho the all-in-one is a better (smarter) solution if you are starting from scratch.