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stepup DC-DC — Parallax Forums

stepup DC-DC

BornaBorna Posts: 36
edited 2010-10-19 07:17 in BASIC Stamp
Hello all,
I have a solenoid rated for 6V. What I want to do is to activate the solenoid initially with 12V for about 1 sec and then bring the voltage down to 6V for 3 sec.

How can I design a circuit with basic stamp to convert 6V to 12V for only a sec and then drop it back to 6V?

Thanks
Borna

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-10-15 20:37
    What is your overriding objective? Is it to issue a positive "jolt" to the solenoid, then to provide a lower holding current so it doesn't overheat? Or is there another reason for doing it this way? Also, what is the coil resistance of the solenoid? I'ts a DC solenoid, right?

    -Phil
  • BornaBorna Posts: 36
    edited 2010-10-15 21:01
    Yes, the objective is to issue a positive jolt as you said and then provide a lower holding.
    I'm not sure yet about the resistance at this time since I'm looking for an idea as how to accomplish this.
    Also this is a DC solenoid.


    Borna
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-10-15 21:52
    If the current in the solenoid is not too high, you can accomplish this with a series resistor equal to the coil resistance of the solenoid and drive it with 12V. Because of the coil's inductance, it will see the full 12V initially. Then, as the current builds up through the coil, it will gradually see less and less voltage as the voltage drop across the resistor increases, finally settling at 6V. Of course, the resistor has to have a sufficient wattage rating to conduct or radiate the V2/R losses gracefully without burning up. That's why I asked about the coil resistance, BTW, to see if this was even feasible.

    -Phil
  • ercoerco Posts: 20,256
    edited 2010-10-16 08:31
    Or get a nice big electrolytic cap and wire it throught a DPDT relay to switch it series- parallel. Make the cap normally charge in parallel with your 6V supply, then when you momentarily trip it, it goes in series with your 6V supply to make 12V. Obviously you need to switch your relay back to 6V before the cap voltage drops to zero, and the relay needs to switch back faster than the solenoid the solenoid can snap back. Will require some experimentation with cap & relay choice, as well as an extra i/o pin, but it's a minimal parts add. Just ask if you need help with the relay wiring. This does work.

    Alt, you could get tricky with a zener diode and make the relay switch itself after the cap voltage drops and save an i/o pin.
  • ercoerco Posts: 20,256
    edited 2010-10-16 09:03
    Relay wiring attached.
    relaysolenoid.jpg
    450 x 400 - 18K
  • BornaBorna Posts: 36
    edited 2010-10-16 11:32
    hey thanks for the diagram.
    Actually I'm very new to electronic and just learning.
    Can I use transistor instead of relay?

    Thanks
    Borna
  • ercoerco Posts: 20,256
    edited 2010-10-16 14:05
    4 transistors, one relay is much simpler!
  • BornaBorna Posts: 36
    edited 2010-10-18 14:04
    Hi, Can you please show me how the circuit looks like with transistors?

    Thanks
    Borna
  • Spiral_72Spiral_72 Posts: 791
    edited 2010-10-19 07:17
    IMO You'd do much better with a relay.... they are a lot more forgiving :) Just a thought.
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