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  1. Alec_t

    Micro controlling resistance

    Nice!
  2. Alec_t

    Micro controlling resistance

    I just used the minimum resistor value in your post #32 list. The value isn't critical, but shouldn't really be zero in case the gauge throws a wobbly (it probably wouldn't) and also to protect the MOSFET in case the gauge somehow got short-circuited. Whatever resistance is used you are going to...
  3. Alec_t

    Micro controlling resistance

    You could use 39 Ohms (a standard value) instead of the 10 Ohm resistor. (But the 10 Ohm would do; just needing a reduced duty cycle to get the same effect as 39 Ohms). The 2.2k stays the same.
  4. Alec_t

    Micro controlling resistance

    If the gauge is some sort of heated element device then I suspect it won't mind in the least having a raw PWM input signal and the cap would be redundant. Give it a try. Edit: Sounds as though the gauge is this type. If so, no cap needed.
  5. Alec_t

    Micro controlling resistance

    I don't know how your gauge would respond to a large 100Hz (or 130Hz) ripple on its input. It will probably hum at you :). It might have enough inertia (assuming it's a moving coil type) to average the varying PWM satisfactorily, mechanically. If not, to reduce the ripple to the amount present...
  6. Alec_t

    Micro controlling resistance

    Looks good.
  7. Alec_t

    Micro controlling resistance

    I think your 10k base resistors in the bit-shifter are too high. To use a bjt as a switch it is usual to assume a current gain in the region of 10-20 only, to make sure that the bjt saturates. A 270Ω resistor will draw about 16mA (if my assumptions about the gauge internals are correct), so the...
  8. Alec_t

    Micro controlling resistance

    From the figures you've provided I calculate that the gauge has an internal voltage regulator of 4.75V (nominally 5V?) and an internal resistance of 53.8Ω. Here's a simulation of a suggested adapter circuit using 5V PWM at a nominal 1kHz rate from an MCU to drive the gauge :- A PWM duty...
  9. Alec_t

    Micro controlling resistance

    That helps. I'll dig out the circuit used in a similar project and adapt it for this one. Might be a day or two.
  10. Alec_t

    Micro controlling resistance

    I have an adapter circuit in mind. What are the voltages across the 240Ω, 153Ω and 10Ω resistors? Better still, a calibration graph of voltages versus all the resistance values would be helpful.
  11. Alec_t

    Micro controlling resistance

    What is the supply voltage to the gauge? Can you post a link to the type of gauge or its specification? Is it a vehicle fuel gauge?
  12. Alec_t

    Shaded pole motor.

    I don't think there is an easy way without sacrificing torque. Can't you use a DC motor?
  13. Alec_t

    welding pit

    I think a soldering bath is intended. Most solders, even high temperature ones, melt below 300°C, so why do you want the bath at 450°C?
  14. Alec_t

    Mobility scooter issue

    Welcome to EP! If the current path through the controller is bad (failed transistor, broken wire, poor connection) the controller would probably sense that and complain. Is one of the brake connections via the scooter chassis? (Corroded ground connections are a common cause of grief in cars.)
  15. Alec_t

    Is hand sanitizer electrically conductive ?

    .... or just transfer the sanitizer to a glass container :).
  16. Alec_t

    Is hand sanitizer electrically conductive ?

    It depends on the ingredients in the product. A bottle I have lists the ingredients as "Alcohol denat, aqua, glycerin, propylene glycol, triethanolamine, carbomer, aloe barbadensis gel, tocopheryl acetate, parfum". My multimeter with probes ~ 1cm apart in a small puddle of it shows a resistance...
  17. Alec_t

    [Beginner] Having trouble using one momentary switch to activate multiple oscillator circuits.

    Welcome to EP! Pictures of breadboards are only rarely helpful. What we need to see is a clear, logically arranged schematic, with component designators (R3, C99 for example).
  18. Alec_t

    Yamaha RX-V483 dead.

    Does the relay pull in? The board is discoloured below the big primary cap, suggesting overheating. Did you measure the ESR of that cap?
  19. Alec_t

    Issues with micro usb connector on circuit board

    Spares are available (here for example), but can't you re-use the original part? The problem will be soldering the contacts. It looks as though two pcb contacts have become detached from the pcb, in which case you may have to scrape off the covering from circuit traces to find somewhere to...
  20. Alec_t

    Drive an heating element for an homemade oven.

    You should NOT be using the element on a circuit protected by breaker 8 or 3. If it's on a circuit protected by any of the other breakers (all rated for 16A or 32A) and the breaker is tripping then the element is faulty and should not be used..
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