Search results

Search Forums New Posts
  1. duke37

    Working with high voltage pulses

    The Massey link would not work for me, perhaps the internet stopped up too late last night. I have mended a few fencers and was given a Gallager voltmeter to check them. I think that using leds is not optimum since they take significant current, however the newer mains fencers seem to have an...
  2. duke37

    Shot counter

    Some time back I saw method of counting turns on a coil winder. A simple calculator can be set to do the same calculation when a button is pushed. Set it up to add one each time and reset it when needed. The trigger would need to be connected to the appropriate button contact.
  3. duke37

    oscillator help

    My first disagreement with Colin was when he said that inductors cost nothing. I found the Colin's comments on this thread by clicking on 'spot mistakes', then P24 then P25. I gave up on this thread, there seems to be no point in arguing when the action of a tuned circuit is not understood. In...
  4. duke37

    Components for this amplifier

    The 10 ohm, 47nF circuit is known as a Zobel network. Speakers show an inductive reactance at high frequencies and the network provides a resistive load at ultrasonic frquencies. This ensures amplifier stability.
  5. duke37

    Making new AC DC transformer for La Z Boy chair

    Sorry, my mind was on another thread. Ah, so it is a DC electric motor with the polarity reversed to reverse the actuator direction. It looks as if it takes 2.2A. Have you measured this at the recommended 24V DC. If you get no action with a couple of amps, then I would suspect mechanical...
  6. duke37

    Drive two relays based on input voltage.

    But the deadband depends on the stability of all voltages and disaster may occur if both outputs are activated. I do not know the effect of the two outputs activated concurrently but some extra protection should be built in There was the case of a prototype electric locomotive which was running...
  7. duke37

    Drive two relays based on input voltage.

    What happens if both solenoids are activated? You may need incorporate some fancy circuitry to stop this, perhaps using an extra contact on the relays.
  8. duke37

    Making new AC DC transformer for La Z Boy chair

    If the lights dim when the actuator is plugged in then current is being drawn, you just have to find out where. A lack of a flywheel diode will give very high voltage on the collector of the switch when it is switched off and could pop the transistor.:( You could try with a resistor instead of...
  9. duke37

    Making new AC DC transformer for La Z Boy chair

    When an inductance like a relay coil, solenoid coil or DC motor is turned off, the energy due to the magnetism has to be dissipated in some way. Normally, a spark would be formed at the switch, this may burn out contact points or fuse semiconductors. A diode placed across the inductance will...
  10. duke37

    I'm a Carpenter, not an Electrical Engineer

    You appear to have two pick-up coils in series. The switch shorts out one or the other to leave one coil doing the business. In the centre positon, the two coils are in series and you get the addition of the two signals. I do not see what the white wire does, it perhaps gives a ground reference...
  11. duke37

    Where do I go now to learn more? (Self taught prop/toy maker)

    You could join a local radio club (see RSGB.org). Some of these give training classes for the examinations to get permission to transmit, these start with the basics. You may find a guru to help you, not all the members are grumpy old codgers like me.:) EDIT You could join a REMAP group which...
  12. duke37

    Making new AC DC transformer for La Z Boy chair

    Have you got the right polarity on the capacitors? Is there a flywheel diode across the solenoid which would conduct if the polarity is wrong?
  13. duke37

    LED Strips Display driven from 555 / 4017 counter

    The inputs to CMOS have very high impedance so they will switch the gate from stray voltages in the vicinity. If the gate goes into fast oscillation, the gate will consume a lot of power and perhaps overheat. Connecting the gate to something stops this wild behaviour. If you use a 4093 gate...
  14. duke37

    Transformers and bridge rectifiers [question]

    The transformer changes 240V AC to 32V AC. In order to get DC it must be rectified which is what the bridge does. The current comes as pulses and these are smoothed by the 3.3mF capacitor. The LM338 regulates the voltage, it does not regulate the current until it is asked to pass more than its...
  15. duke37

    Making new AC DC transformer for La Z Boy chair

    Does the capacitor have a domed end? if so it is likely to be faulty. The 34.4V will drop under load so the 35V capacitor should do.
  16. duke37

    Thermostat

    The 25V capacitor is an electrolytic with a value of 100μF, that is all you need to know. There are capacitors which can run at higher temperatures. The 'box' labelled 474 is likely to be a capacitor of value 47 with 4 noughts in other words 470 000 pF (about half a μF). I expect this is...
  17. duke37

    Edgestar ap12000hs-1 thermostat not working

    If the stat shows the correct temperature, then I would suspect that the detector has been displaced and is too close to the heater.
  18. duke37

    Bench power supplies! [help!]

    It all depends on what you want to do. To drive a powerful transmitter you should go for a comercial 13.8V, 30A supply. To test small circuits, a PP3 9V battery is best. Operational amplifiers often use +12 to 15V/ -12 to 15V Other circuits work on 5V or even less. Switch mode power supplies...
  19. duke37

    Thermostat

    No, no no !!! I = V/R Learn Ohm's law !!! This drives a heater not a motor. Trevor
  20. duke37

    Ring modulator in multisim doesnt work as real life (or at all)

    A ring modulator has the diodes chasing their tails. D1 and D2 are connected like a diode rectifying bridge.
Top