JackH Posted September 29, 2004 Report Share Posted September 29, 2004 Hello All, I have a question, and would be very gratefull if some one could help. I am currently working on a new type of DC electric motor, the current version of this motor uses a set of motor cycle points to turn the coils on/off, causing alot of drag and arcing across the points. Was wondering if the MOSFET circut that I have drawn up will work instead of the points. And if so could some one tell me what the R1 and R2 resistence should be. Or if the circut needs totally changed. Quote Link to comment Share on other sites More sharing options...
hotwaterwizard Posted September 30, 2004 Report Share Posted September 30, 2004 Is there a Timing or a Pulse Width Modulator circuit to turn the Coils on and off? I personally don't like MOSFET because it is static sensitive.You have 2 coils attached to a Static Sensitive Device.These coils cause Reverse Spikes as the Fields colapse. Also EMF Waves. I just don't like the Idea.How about a Electronic Ignition type Circuit Instead using Discrete Transistors like a 2N3055. Quote Link to comment Share on other sites More sharing options...
JackH Posted September 30, 2004 Author Report Share Posted September 30, 2004 hotwaterwizard,The coils are fired with the opto sencer. A small disk is mounted on the motor shaft with two slots cut in it. This disk turns the opto sencer on/off. For every revolution the motor turns the coils should fire twice. I kinda thought the mosfet would work better because of the reverse emf diode it contains. This diode returns some power back to the battery when the coils colaps.However I am not picky, If you have a better idea for the control circut I would really like to see it.Thanks,,,,Jack Quote Link to comment Share on other sites More sharing options...
hotwaterwizard Posted September 30, 2004 Report Share Posted September 30, 2004 How about just Installing some MOV's and or Protection Diodes.Or even an Isolation Transformer or a Triac o Solidstate Relay. Quote Link to comment Share on other sites More sharing options...
JackH Posted September 30, 2004 Author Report Share Posted September 30, 2004 Well, This may help but I am new to electronics and am not familar with any of the items you mentioned.I might add, This motor run's at over 5,000 rpm, the coils need to be powered two times per revolution of the motor, so they will need to be powered on/off at over 10,000 time per minute.To make a little more clear. I need someone to look up the H21A1 opto sencer from www.fairchildsemi.com and find out the voltages it needs at the anode to light up the diode. Also need to know how much voltage the mosfet needs at the gate to open it up. And how to setup the circut to get these voltages when using 36 vdc at the input.Any and all help would be appreciated.Later,,,,Jack Quote Link to comment Share on other sites More sharing options...
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