Post by thread:Motor Feedback

part 0 6014 bytes I have an autohelm for my sailboat that I would like to replace the "smarts" with a PIC.  The motor has a small circuit board attached to it that I feel is some sort of feedback circuit.  My analog skills have never been a strong point, and wanted to take advantage of the list to see if someone out there could give me an educated guess to this circuit.  I contacted Maxon to see if it was one of their feedback units, but they stated that motor was a special order with no feedback.  The unit runs from 12vdc Thanks David                       Red                        |             27 ohm     |     .3 ohm power resistor Yel -----/\/\/\/\/\----|----/\/\/\/\/\/--|       |                                  |       |      220 ohm                     |       |----/\/\/\/\/\/----|---Motor------|                           |                      |----------|                      |          |                    Blue       Green Just in case the ASCII art gets distorted,  there is a yellow wire that feeds a 27 ohm and a 220 ohm resistor. The other end of the 27 ohm goes to a red wire and a .3 ohm power resistor. The other end of the 220 resistor goes to one terminal of the motor, and to a Blue wire and a Green wire.  The other end of the .3 ohm power resistor goes to the 2nd terminal of the motor. </UL> Are you absolutely sure that the blue and the green are tied together?  My first guess would be that the 0.3R resistor is for current measuring purposes, and the 27R and 220R provide a reference voltage to the control electronics.  However, to sense current there would have to be a wire comming from the junction of the 0.3R resistor and the motor. Cheers Mike </BODY> </HTML> </x-html>

Michael - I think I have it ringt, but will try to re-check tonight. Thanks, David -----Original Message----- From: Michael Rigby-Jones [spam_OUTmrjonesTakeThisOuTNORTELNETWORKS.COM] Sent: Tuesday, February 08, 2000 9:31 AM To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU Subject: Re: Motor Feedback -----Original Message----- From: Fansler, David [SMTP:DFANSLERKILLspamAUTOCYTE.COM] Sent: Tuesday, February 08, 2000 1:52 PM To: .....PICLISTKILLspam.....MITVMA.MIT.EDU Subject: OT: Motor Feedback I have an autohelm for my sailboat that I would like to replace the "smarts" with a PIC. The motor has a small circuit board attached to it that I feel is some sort of feedback circuit. My analog skills have never been a strong point, and wanted to take advantage of the list to see if someone out there could give me an educated guess to this circuit. I contacted Maxon to see if it was one of their feedback units, but they stated that motor was a special order with no feedback. The unit runs from 12vdc Thanks David Red | 27 ohm | .3 ohm power resistor Yel -----/\/\/\/\/\----|----/\/\/\/\/\/--| | | | 220 ohm | |----/\/\/\/\/\/----|---Motor------| | |----------| | | Blue Green Just in case the ASCII art gets distorted, there is a yellow wire that feeds a 27 ohm and a 220 ohm resistor. The other end of the 27 ohm goes to a red wire and a .3 ohm power resistor. The other end of the 220 resistor goes to one terminal of the motor, and to a Blue wire and a Green wire. The other end of the .3 ohm power resistor goes to the 2nd terminal of the motor. Are you absolutely sure that the blue and the green are tied together? My first guess would be that the 0.3R resistor is for current measuring purposes, and the 27R and 220R provide a reference voltage to the control electronics. However, to sense current there would have to be a wire comming from the junction of the 0.3R resistor and the motor. Cheers Mike

part 0 6053 bytes After reviewing the circuit mounted to the motor, I did find an error - so here is the revised schematic.                       Red                        |             27 ohm     |     .3 ohm power resistor Yel -----/\/\/\/\/\----|----/\/\/\/\/\/--|       |                                  |       |      220 ohm                     |       |----/\/\/\/\/\/----|---Motor------|                           |              |                           |              |                           |              |                         Blue           Green Just in case the ASCII art gets distorted,  there is a yellow wire that feeds a 27 ohm and a 220 ohm resistor. The other end of the 27 ohm goes to a red wire and a .3 ohm power resistor. The other end of the 220 resistor goes to one terminal of the motor, and to a Blue wire.  The other end of the .3 ohm power resistor goes to the 2nd terminal of the motor and a Green wire. </UL> This is more than likely a protection scheme to limit the current to the motor.  The 27R and 220R resistor provide a reference to the control circuitry.  By placing these devices in close proximity to the motor, any voltage drops in supply cables are ignored.  The current limit will probably become active when the voltage drop across the 0.3R resistor exceeds that accross the 27R resistor. I=(V*(27/247))/0.3  where V is the supply voltage. Your original post asked if this was some kind of feedback circuit.  Well it is in a sense, but it dosen't feedback positional information, only current draw Cheers Mike. </BODY> </HTML> </x-html>

On Wed, 9 Feb 2000 13:34:03 -0000 Michael Rigby-Jones <EraseMEmrjonesspam_OUTTakeThisOuTNORTELNETWORKS.COM> writes: {Quote hidden}> Fansler, David [DFANSLERspam_OUTAUTOCYTE.COM] wrote: > > > After reviewing the circuit mounted to the motor, I did find an > error - so > > here is the revised schematic. > > > > Red > > | > > 27 ohm | .3 ohm power resistor > > Yel -----/\/\/\/\/\----|----/\/\/\/\/\/--| > > | | > > | 220 ohm | > > |----/\/\/\/\/\/----|---Motor------| > > | | > > | | > > | | > > Blue Green > > > > Just in case the ASCII art gets distorted, there is a yellow wire > that > > feeds a 27 ohm and a 220 ohm resistor. > > The other end of the 27 ohm goes to a red wire and a .3 ohm power > > resistor. > > The other end of the 220 resistor goes > > to one terminal of the motor, and to a Blue wire. The > > other end of the .3 ohm power resistor goes to the 2nd terminal of > the > > motor and a Green wire. > > > > > This is more than likely a protection scheme to limit the current to > the > motor. The 27R and 220R resistor provide a reference to the control > circuitry. By placing these devices in close proximity to the > motor, any > voltage drops in supply cables are ignored. The current limit will > probably > become active when the voltage drop across the 0.3R resistor exceeds > that > accross the 27R resistor. > > I=(V*(27/247))/0.3 where V is the supply voltage. > > Your original post asked if this was some kind of feedback circuit. > Well it > is in a sense, but it dosen't feedback positional information, only > current > draw > > Cheers > > Mike. If it does feed back current...then the chip probably calculates the speed from it.. Andrew ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: dl.http://www.juno.com/get/tagj.