Power issues

Discussion in 'General Electronics Chat' started by E-MotionRichard, Aug 26, 2014.

  1. E-MotionRichard

    Thread Starter New Member

    Aug 26, 2014
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    Greetings fellow techs. I am currently a student finishing up my senior year in Electrical Engineering. At work, I work with motion controls. Currently I have a project that I am working on, where our engineer designed a board to interface with a controller/driver. The circuit basically consists of a couple resistor, voltage regulator, diode and relay. When testing interface board alone, all voltages measure correct. However, when connected to the controller/driver, the voltage drops to 1.8 Vdc, instead of the 24Vdc input that it should be. Could this be an isolation problem? any input would be appreciated.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A little more info needed, like a diagram or schematic maybe?
    Max.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    yes isolation problem.. in that we are "isolated" from virtually all the needed information to help :)
     
    MaxHeadRoom and wayneh like this.
  4. E-MotionRichard

    Thread Starter New Member

    Aug 26, 2014
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    Thank you for your replies, yes, I guess I failed to share that vital information. At the moment, I do not have the schematic with me, but will share a little more info. As stated, the circuit our engineer designed consists of only 5 components, (a regulator, two resistors, a diode and a relay). Also, there are 7 connectors on the board (a 4 pin header, 5 pin header, two 8 pin headers, a 4 pin molex connector, a 14 pin connector, and a DB 15 connector).
    The control board, which I do not yet have a schematic for, has four connector as well that we connect to. Our 4 pin, 5 pin, and two 8 pin headers plug into the matching connectors on the control board.
    Ok, now a little about the circuitry. Without our interface board, our two phase stepper motor connects to one of the 8 pin connectors on the control board (A+, A-, B+, B-). The 4 pin connector is: +24VDC, GRD, RS485 A, and RS485 B. Then the 5 pin connector is for the encoder, +5VDC, GRD, A signal, B signal, and Index. The other 8 pin connector we are not using, but it is for inputs.
    On our interface board, we bring the power and RS485 signal in through the DB 15. The +24VDC feeds through to the power connection of the control board, and also powers the regulator. The regulator is four pins, pin1-ADJ, pin2-Vout, pin3-Vin, pin4-Vout. Pins 2&4 go to the cathode of D1, and also to the coil of the relay, the anode and other end of relay coil go to GRD. Then there is R1, a 1.5K ohm resistor, one end goes to the output of the regulator, and the other end goes to ground. There is also a 240 ohm resistor, R2, which I can't remember the connection without the schematic in front of me. The encoder connections go through the 14 pin connector and feed straight through to the control board. Next, the A & B phases of the stepper motor go through the 4 pin molex connector, through the contacts of the relay, and then to the 8 pin connector of the control board.
    Hope this info helps you understand a little more what is going on with the circuit. If needed, I will try to attach the schematic while at work tomorrow. Thanks in advance for any suggestions you may have.
    Richard
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Not really!

    But did I gain the fact that you are attempting encoder feedback for a stepper motor?
    Max.
     
  6. E-MotionRichard

    Thread Starter New Member

    Aug 26, 2014
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    Yes Max. Not attempting, succeeding with encoder feedback with the stepper motor. Without the new interface board, everything works great. However, with the interface board, nothing works. Basically, all the interface board is for, is to use the relay as a break for the stepper motor. As I said though, the interface board is just a simple regulator circuit powering a relay. My guess is that there is some feedback from the interface board that is causing the voltage to drop.
     
  7. E-MotionRichard

    Thread Starter New Member

    Aug 26, 2014
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    The regulator is a LM317M. Vin is pin 3, which ties into the +24VDC of the control board. Pin 2 is Vout, which connects to the cathode of D1, one side of the coil on the relay, and one end of a 240 ohm resistor (was wrong earlier about the resistor). The other end of the 240 ohm connects to pin1 of the LM317M and also to one end of R1, the 1.5K ohm resistor. The other end of R1 connects to the anode of D1, and the other end of the relay coil, which all connect to ground, which ties into the ground of the control board. When connected together, the voltage drops significantly.
     
  8. E-MotionRichard

    Thread Starter New Member

    Aug 26, 2014
    7
    0
    Max, Thanks for your replies. I ended up just emailing the engineer that designed the circuit, and found the problem. The problem was with the design. An LM317 regulator cannot direct drive a relay, there needed to be a capacitor parallel with the D1 diode. Thanks again for trying to help anyway.
     
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