Identify This Component

[bostonman]

Does anyone know what this component is? It's a three terminal device that's in a saw that doesn't turn on - measuring across the plug doesn't go to low resistance when I squeeze the switch indicating something is open.

From what I can tell, both hot and neutral from the input power go into the switch (the switch has five wires connected to it). The hot (I believe) comes out of the switch (the switch connects these two together) into one of the poles (?), out of the pole, into the next pole, out of the pole, and to a brush.

Another wire from the switch goes into this component and I believe a second wire comes out and goes to the other brush.

The brushes seem to make contact with the armature and it doesn't seem any coils are open. I'm thinking this component is some sort of heat sensor that opened.

The switch could be bad since it has five wires and I'm uncertain which wire(s) get shorted together.

[fzabkar]

FWIW, I found this:

https://www.mmtoolparts.com/store/milwaukee-remote-electronic-assy-14-20-3015

[bostonman]

Wow, that's a help for sure, however, I don't know what a remote electronic assembly is.

This is a hand held power (reciprocating) saw and doesn't have any remote capabilities.

[fzabkar]

Is the speed variable?

Maybe the part is a triac whose gate is controlled by the switch. In this way the motor current would be handled by the "remote" unit rather than the switch contacts. That would make it a solid state relay of sorts.

[bostonman]

Hmmm I think it did - it would have been dependent on how much the trigger is pulled.

It's one of those 'features' that you don't pay attention to until you need to question it.

[fzabkar]

Then maybe the speed control circuitry is inside the switch, and the MEC part is just a triac.

https://patents.google.com/patent/DE3045610A1/en

The driving motor supply is regulated by a triac whose gating signal is controlled by the finger operated trigger switch of the drill. The triac is mounted on a heat sink and the whole assembly placed in the inlet air duct to the motor cooling fan. Using the intensive cooling thus provided the triac can be operated safely at full motor current demand continuously. The trigger switch can therefore be employed as a gate signal controller only without any current making or breaking duty. This greatly eases the duty on the switch and also eliminages electrical disturbance when the switch makes or breaks current. The triac can also be used as a simple on-off switch without providing speed control.

[bostonman]

This is a big help, thanks.

I was using this saw under a load and it stopped working. Initially I thought it had a thermal switch inside that kicked out, so I waited. Within about ten-minutes the saw began working again.

After I was done, I unplugged it and put it away. A few weeks later (last week) I went to use it and it didn't turn on.

I thought maybe a broken wire (extension cord or something inside), but the wires seem fine. Unfortunately the switch has five wires connected to it (both hot and neutral go to it), so I don't know which ones get connected. Now that I know it may be a poteniometer, I'll try measuring some of the pins to see if the resistance changes.

[bostonman]

Tonight I mapped the wires, and, going under the assumption the three-terminal device is a Triac, I drew a schematic.

Just wanted the input of others to check whether this looks accurate. Also, I assume the Triac is being used to handle the current rather than the switch dropping the voltage. Is that the purpose of this Triac?

Just an FYI, I think the problem with this saw is the switch because the terminal that varies from 24k to 300k is intermittent. I assume the variation in resistance is typical and that drives the Triac's gate to pass more/less current?

[Gyro]

That's more than just a triac then - it will be a (potted?) speed control module with multiple components inside. You're best looking for the tool manufacturer's part - or an after-market substitute.

[bostonman]

I think the switch is bad.

From what I can tell, the switch isn't always varying from 24k to 300k unless I wiggle the solder post.

As for the function of the Triac, I began simulating it last night and had issues. From my understanding, the switch in this case would need to supply voltage before the Gate turns on, else, the motor will not turn on until the switch is squeezed more. If that's the case, then the motor would start faster.

I need to measure where the switch engages. From what I understand about Triacs (I've never used them), the gate gets turned on, voltage can be removed from the gate, and the Triac will still conduct until the main voltage is removed.

From what I *thought* I measured, the two on/off portions of the switch don't switch on until the switch is squeezed all the way, however, I believe voltage should be on the terminals of the Triac before the gate begins lowering in resistance.

[fzabkar]

What is the model/make of the saw?

Are there any patent numbers on the label or in the user manual?

Do you have any idea how old it is?

I'm assuming that the make is Milwaukee Electric Tool Company.

[Squoip]

It's for a Milwaukee saw. The Milwaukee part number is 14-20-3015. They are available from any number of sources for under $20.

[bostonman]

It is a Milwaukee saw, however, the plate is scratched and the model/serial are rubbed off; but it's an older model.

The problem was the 'gate' wire on the switch wasn't making good contact. Initially I thought it was internal to the switch, so I disassembled it. Now, after learning how the switch works, I've begun re-assembling it.

For whatever reason, I created two identical Triac circuits using the same part number in both MicroCap and MultiSim and MultiSim isn't turning on the Triac.

Having never used a Triac, I thought simulating one to learn more about them would be good, but I can't figure out the error in MultiSim. I attached the circuit should anyone have input on where I went wrong.