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jraef, I will look forward to hearing from you. cbarn, Thanks for the suggestion. However there are two issues with putting something near the teeth of the blade. First, the blade can be deflected by an 1/8 of an inch or more, so you can't be very close. That makes it hard to accurately...

jraef, It turns out that on a table saw the blade will continue to coast for 10 seconds or longer after you shut off the saw. There are a fair number of accidents during this period of coast down. We therefore need to have our contact detection system active during this period. However, someone...

Have you tried drill motors? I would think the average hand drill would be a universal motor about this size.

jraef, First, it is good news to know that it can be done - however, the real question is can we switch and brake the 1.5 hp motor for $5 or so. Second, it might be that you had the requisite knowledge and could share it without feeling like you were giving away some type of trade secret. I...

tmahan, Do you happen to know how these devices are sensing zero speed? It seems like it should be easier to detect rotation with the DC applied than if the motor was just coasting, however, the DC in an injection brake is pretty ugly to begin with it seems like, so extracting the back emf...

cbarn, I'm not looking to design it myself, but rather understand the operation to so that I can help plan overall design with someone more knowledgeable. I'd be happy for any suggestions of a knowledgeable design consultant in this area as well. But back to the question, where is the diode...

Don, Thank you for the suggestion. I am hoping to have something that doesn't require any extra cabling to minimize cost. This is for a consumer product and every dollar is critical. What I am trying to replace is a IR opto detector pair that looks through a hole in a shaft spun by the motor...

cbarn, Thanks for the suggestion. I think I understand the contactor - cheaper than a triac I suppose, and the thyristor is used like I was thinking to use half the triac, but what is the "flywheel diode" and how is it arranged in the circuit? Also, do you have to have a current sense...

Any suggestions for the cheapest (a few dollars) way to implement DC injection braking (or other braking) in a motor control circuit? All we need in the circuit is on/off control and we are considering a triac or a relay. I have wondered if we could simply drive the triac during one half cycle...

1. Is it possible to reliably sense motor rotation from back EMF during coast down to determine when the motor has stopped rotating? 2. Will we see similar or at least some back emf with all typical single and three phase induction motors in the few horsepower range? 3. If the answer to...