Tracking Board Encoder and Carving/Cutting bits on A and B series Machhines

[lynnfrwd]

I do not know why some would take longer to slow down then others, but I do know the reason for the spin-up. With the old quick change chuck, if you didn't get the bit seated properly, the spin-up would make the bit fall out rather than going into the wood at full speed and shooting it out.

I was also told that everyone should make sure their software is up-to-date and not using older versions.

Also, I sent a link to this thread to an engineer to look at.

From what I understand, all B & C machines had the metal clip on the encoder.

[bergerud]

So that is the reason for the spin up. Interesting. And then, just before the bit hits the wood, the machine winds up to the max. I always thought that was to seat the adapter into the QC by throwing out those half rings against the taper in the top of the QC.

Anyway, I find it hard to believe that the large difference between machine spin downs can be explained as differences in friction. It seems feasible to me that large voltage spikes from opening the cover when the machine is running could take out the capacitor in the snubber circuit and lead to the condition where the triac cannot simply shut off. It is just a theory and it is easily disproved by someone with the spin down problem. All one has to do is compare the spin downs when the machine shuts off the cut motor versus a manual shut off of the cut motor. If these spin downs are the same then the theory is out (sorry). If the spin times are quite different then it means the machine is not powering down the cut motor as it should and the capacitor is suspect.

[lynnfrwd]

I don't have a clue Bergerud...you are talking a different language than I can understand.

I'm just glad the most active topic is of something that doesn't even effect ones ability to carve or use the machine.

[ibewiggin]

Amen to that Connie!

[ibewiggin]

http://www.youtube.com/watch?v=weRDRxo9VQU

Here you go, sorry it took so long!

[grinanbarrett]

I don't have a clue Bergerud...you are talking a different language than I can understand.

I'm just glad the most active topic is of something that doesn't even effect ones ability to carve or use the machine.

LOL No kidding, I have to totally agree with that!

[bergerud]

Thanks for the video. (You should watch mine again.) My motor gets a short on-off and the spins down fairly quickly. Yours gets a much longer pulse which drags on. What I see backs up (actually does not refute) my theory. Let me explain it again. The cut motor is turned on by a small signal from the computer to the gate of a triac. A triac is a remote controlled semiconductor switch which, once turned on, waits until the ac cycle zeros and then turns off. To keep it on, the computer has to keep the voltage signal on the gate. The problem comes when the gate signal stops. The triac should turn off within 1/60 of a second. If it was running a light bulb it would. It is instead running and inductive motor which produces a back emf (high voltage zap) if you try and disconnect its power. This back voltage acts like the signal did and turns the triac back on. To overcome this problem with inductive loads, a circuit called a snubber circuit is installed. This circuit consists of a capacitor and resistor in series placed across the triac switch. The snubber protects the triac from the motor signals that would turn it on.

Now our snubber capacitor has a break down voltage of 400 volts. Voltage higher than 400 volts can zap through the capacitor damaging it and making the break down voltage of the capacitor even less. If the capacitor is damaged or not rated high enough, the triac will turn back on. I think the reason that your motor gets a longer pulse than mine is because the triac is having trouble turning off. The capacitor cannot stop the voltage pulses from the motor. There is a feed back game between the motor and the triac which keeps the motor going even though the computer has stopped sending the signal. The feed back dies out as they send smaller and smaller signals back and forth and finally the motor stops.

It would not be far fetched (I know this is all far fetched!!) to think that the opening of the cover switch on our machines while the motor was under full load would produce a voltage pulse far beyond the 400 volt rating of the capacitor. After the capacitor has been "burned", it would have a much smaller break down voltage and then the normal back voltages produced by the motor would be enough to cause the feedback.

It is just a theory! It is up to you guys to test it. If it were my machine, I would solder in a capacitor rated at 1000 volts and see what happens.

It would be nice to hear from LHR on this. Am I crazy?

Normal B machine operation: www.youtube.com/watch?v=cGlfKrin_zA

[Digitalwoodshop]

Interesting Theory with some very good facts.... I have a bag of Caps.... IF I had time to spare I would do the test and solder in a new cap and see what changes.....

2 AM and I am working on 3 Tag orders all due on the 7th..... Almost 300 tags.... Quitting time, checking the Forum..

We may get another Member and User... I am trying to talk my Wood Worker Neighbor into taking over my Sign side of the Business... Don't have time for it....

AL

[bergerud]

I was hoping for a response from LHR on my theory about this spin up problem. Maybe they have tried replacing controller board to solve the problem? I was also hoping someone might replace their C1 capacitor (0.1 micro Farad 400v) in the motor control board and see if this capacitor really is the cause of the problem.

I am convinced that the difference in machines is not because of friction. Ibewiggin's video compared to mine shows that there is a different pulse time. After watching ibewiggin's video a few times, I even think I can hear a difference in motor sound which starts at the same time my pulse would have ended.

In case you are wondering just what part I am talking about, here is a picture of the controller board courtesy of Al. The capacitor in question is that big brownish orange blob.

[liquidguitars]

The video shows the QC engagement spin, but at times I get a spin when lifting the hood, I remember talking to Chris L of LHR years ago about this and he seemed not to have a issue overall about it. We all know caps hold charge so it's prob just that or static discharge