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  1. duke37

    Multiple mosfet driving

    I think that they can all be connected to the same emitter follower. The gate resistor is said to damp radio frequency oscillations but I have not had this trouble without the resistor.
  2. duke37

    Cheap Motion sensors , chinese I think

    There seems to be a twiddle pot, RV1. What does this do?
  3. duke37

    Old Silicon Chip Magazine project. Solar/Wind controller

    I would look at C7/R16. C7 should be discharged in 10 or 20 seconds. If this is not done, then switching on for the second time will put too much voltage on the 4011 input. A high value resistor on the 4011 input would protect it without affecting the operation. Check that the supply voltages...
  4. duke37

    Power Amplifier for thermoelectic cooler with Op-Amp and Power MOSFET PROBLEM

    That is how all amplifiers work. The only component that can increase or decrease a voltage or current is a transformer which can trade voltage for current with some loss. The power has to come from somewhere.
  5. duke37

    Power Amplifier for thermoelectic cooler with Op-Amp and Power MOSFET PROBLEM

    10V / 205k = .0.05mA input.
  6. duke37

    Circuit analysis

    We do not do your homework. We can help if you do not understand a particular detail.
  7. duke37

    repair parts

    Have you found the fault? The parts may be standard and can be sourced from many places.
  8. duke37

    Power Amplifier for thermoelectic cooler with Op-Amp and Power MOSFET PROBLEM

    The 0.33Ω resistors are even in the E6 series. Using two resistors splits the power so smaller resistors can be used. Have you tried to get a 0.165Ω resistor? The three MOSFETs are very similar and any one could be used. The IRL1530N has a slightly lower on resistance. The RFP12N10L has a...
  9. duke37

    Power Amplifier for thermoelectic cooler with Op-Amp and Power MOSFET PROBLEM

    Firstly, the power supply is rated for 3A and the cooler requires 6A. Something will or has gone pop. The control signal is attenuated by the two resistors so 10V input will give 0.483V at the op amp. The opamp will turn on the MOSFET until the other input also gets 0.483V. This achieved when...
  10. duke37

    Car Battery/Car Alarm/Capacitor Question

    See KTW #5. You cannot test the capacity in a battery with a voltmeter. You need to find the drain current and see how much of the battery capacity has been used up. Why does Greenland have a red flag?
  11. duke37

    12vdc low amp to 120vac high amp flash/blink lamp inverter circuit?

    To go from 12V to 120V you will need a substantial invertor. to charge the capacitor and a SCR or fet for a switch. The life of the bulb could be short since the very high current which is necessary during switch on can fuse the hottest part of the filament. Photofloods are turned on gradually...
  12. duke37

    Attatching controls to popcorn machine.

    A lamp dimmer could well be used to control the speed of the fan but I doubt if a dimmer could be man enough to supply the heater. Have you thought about what would happen if the fan speed was set too low?
  13. duke37

    Current/heat dissipation control in an R-L circuit

    Your DC power supply uses high frequency switching.
  14. duke37

    Need Help Identifying Collector, Emitter, and Base

    A fet will work as a replacement for a bjt. You will need less control current but much more voltage. You still have not shown a schematic (US).
  15. duke37

    Car Battery/Car Alarm/Capacitor Question

    Surely your trouble is the temperature of the battery. One crank will warm the battery for the second crank. Use thin viscostatic engine oil. An auxilliary warm battery will do better than a capacitor with very limited energy. Park your car over a volcano.:)
  16. duke37

    Basic Soldering advice

    I keep my reel of solder in a plastic bag with the end of the solder coming out through a hole. This stops my sticky fingers from corroding the solder and stops me picking up lead. Cleanliness is critical.
  17. duke37

    Electrostatic air cleaner

    The cap comes from 1983. It is labelled MFD, they do not mean this. Nowadays it would be labelled μF. 0.013 MFD is likely to be 13nF. Also they do not mean 4KV, it should be a lower case k. I do not know where you can find one, perhaps a higher voltage DC cap would do. Comment The editior...
  18. duke37

    Is there a circuit that can energize a coil on 110v, and to keep coil de energized on 220v.

    I get most of my parts to play with from junk sales and old circuit boards, I am not going to look up catalogues for suitable parts. I would not use a DC relay, it will be slower than the AC relay and needs driver circuitry which will give complication and more delay. By diddy I mean small...
  19. duke37

    Is there a circuit that can energize a coil on 110v, and to keep coil de energized on 220v.

    The voltage at which the change over occurs should be a little above110V. A delay on powering the PSU can be generated with a NYC thermister allowing the relay to get there first. I have just bought some 10Ω 2A thermisters but have not yet played with them. I cannot do a schematic at the...
  20. duke37

    Is there a circuit that can energize a coil on 110v, and to keep coil de energized on 220v.

    I have some 230V AC relays OMRON MK2P or NOSLO, 32 * 32 * 48mm plus international octal contact pins, length 14mm. I also have some similar naked ex equipment relays which are slightly smaller without their coats. They all pull in and drop out at 130V AC, 50Hz. A series resistor will increase...
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