(Noob Q) One PSU for Steppers + Controller + Laser

Discussion in 'The Projects Forum' started by Capitaaan, Jul 1, 2013.

  1. Capitaaan

    Thread Starter New Member

    Jun 12, 2013
    2
    0
    Hi, I am currently designing a little laser cutter and so I have two stepper motors, the controller electronics (2x L297+L298 driver) and a 1W laser diode that needs 2V.

    I plan on running the 0.9deg/step steppers at 24V and 0.5mA, the laser at 0.5A and 2V and the controller needs a 5V supply too, the power supply I want to use is a 24V 2.2A laptop charger. My idea is to use voltage dividers to get voltages slightly above 2v and 5v and use an LM317 and 7805. I have read that the motors being an inductive load can cause a lot of noise so i am a little confused.

    I have the complete driver schematic, the 5v and 24v are separate at the moment but I will combine if its possible, you can ignore the optocoupler and transistor part as ill start a seperate thread for that unless you really want to point out any problems it has.

    I would greatly appreciate any help, I need to start building this soon.
    Thanks
     
  2. w2aew

    Member

    Jan 3, 2012
    219
    64
    You'll have to re-think your supply scheme - the voltage dividers won't work. The lower voltage power supplies will draw current, which will be pulled through the upper resistor of the voltage divider, thus increasing the drop across that resistor and dragging the divided voltage down. Switching regulators would be a better way to go.
     
  3. Capitaaan

    Thread Starter New Member

    Jun 12, 2013
    2
    0
    Hi, I have updated the schematic and attached it, currently I want to keep it simple and use a linear regulator but if it wont work then ill go into a switching regulator, I have read that their layout on the pcb is critical.

    I hope that the power supply set up now is fine and have shown the calculations in the schematic, my 7805 dissipates 2.8W so I will use a large heatsink. I have also heard about low dropout regulators but wouldn't they dissipate the same amount as the input is still 9v and output 5v with the same current draw?

    I hope my laser driver circuit is ok, would appreciate any advice.
    Thanks
     
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