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  1. M

    How to control 700 solenoids?

    Thanks, probably right, but don't car injectors, which are very fast cycling, use the high current pulse/hold current solution?
  2. M

    How to control 700 solenoids?

    When switching solenoids you need a high initial current pulse followed by a smaller holding current. This greatly reduces the power consumption and will also extend the life of the solenoid.
  3. M

    Transformer help

    What is it for? Post some photographs of it.
  4. M

    Replacement for TIP120 Transistor

    You need to specify voltage and current ratings for the valves. Off the cuff though I would probably look at surface mount power MOSFETs. They do need overvoltage protection though.
  5. M

    High Voltage

    There are a lot of wires to the connector so it is possible that more than a simple voltage supply is needed to get it working. I would expect an enable signal would be necessary plus possibly others.
  6. M

    High Voltage

    Look for the filter caps. They would tend to place some local to the board.
  7. M

    Control 24v stepper with motor shield

    The optos only provide voltage isolation, they cannot drive the stepper motor, you need power devices like FETs or BJTs for that.
  8. M

    Control 24v stepper with motor shield

    Optos are fast enough. They only need to go to about 50kHz, and you can clean up the output with a schmitt buffer e.g 74HC14.
  9. M

    What is your favourite type of component?

    Only one thing better than a BJT is a matched pair of BJT's.
  10. M

    Cathodic Protection

    Yes I think you are correct. I am only basing my statements on how batteries and circuits work so might be worthwhile double checking.
  11. M

    AD624AD alternative wanted.

    The AD624 is probably worth the money because of the integrated resistors, boosts the CMRR a lot!
  12. M

    Need a tiny tiny DC to AC inverter, or pulsed DC, ideas?

    If you go back to the original link I posted it will explain how to calculate the frequency etc.
  13. M

    Cathodic Protection

    Yes, but the water must carry the return current. A current loop has a to and from, it would be like attaching only one battery terminal and expecting a current to flow.Impossible! You need both connections, and that is what the immersion in the water provides.
  14. M

    What is your favourite type of component?

    Small signal BJT. Incredibly versatile.
  15. M

    Cathodic Protection

    I am guessing, because the water/metal is the electrically active corrosion, so you need the anode/water to make the electrically active anode sacrifice. If the anode is outside you wont complete the circuit, electrically.
  16. M

    Need a tiny tiny DC to AC inverter, or pulsed DC, ideas?

    I am sorry but I don't understand anything you are saying. The circuit which I have copied from the instructable would probably work from 3v DC or could be modified too.
  17. M

    Need a tiny tiny DC to AC inverter, or pulsed DC, ideas?

    You probably need a resonant supply. Will look to see if I find something. P.S. Look at http://www.instructables.com/id/Low-Power-Wireless-Charging/step1/Theory-of-Operation/
  18. M

    Need a tiny tiny DC to AC inverter, or pulsed DC, ideas?

    You can create a coil out of PCB traces. Low profile but not much inductance, unless you use ferrite cores specially designed for it.
  19. M

    Power Inverter

    Total power is 300 watts. It's either 12v dc or 24v dc to 110v AC @ 60Hz, depending on whether you have 24v or 12v dc in your boat. At 12v and full load your current will be around 25A. Such a system with the sound turned up can fairly quickly flatten your batteries.
  20. M

    Vishay Make Quad OPTO SFH6916 Failure

    If it is contamination on the PCB, Bob Pease recommends using a dishwasher! No joke. Then baking in an oven at 160 degrees. Not sure if it was F or C, and not sure if the boards were populated or blank, but probably blank.
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