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  1. Alec_t

    Make one circuit current track with another circuit current

    The switching threshold in the above circuit would be somewhat temperature dependent. To make things less finicky you could incorporate a comparator and trim-pot, like this:- Note that current sensor R3 is now in the ground line.
  2. Alec_t

    Make one circuit current track with another circuit current

    Good to know it works for you, even with a 3Ω resistor dropping significant voltage. I was under the impression that the lamp was supposed to indicate an over-current fault, rather than normal running current. That's why the max value of R1 in the sim was 2.2Ω.
  3. Alec_t

    Where can I simulate AC circuits?

    LTspice (a free download from Linear Technology).
  4. Alec_t

    How can I swap a stock piezo buzzer for a louder 140db buzzer?

    Welcome to EP! The problem is that the piezo disc you ripped from the attack alarm needs an oscillator circuit to drive it (i.e. the remainder of the alarm). The buzzer that came with the kit has the oscillator circuit built in. So it's not just a simple matter of swapping the buzzer for the...
  5. Alec_t

    Help with calculating Hz in a siren curcuit

    Not a good book then :(.
  6. Alec_t

    Help with calculating Hz in a siren curcuit

    Looks like it. Can you post the formulae that the book uses?
  7. Alec_t

    Help specifying a replacement transformer

    Ask yourself why those components failed. Have you checked that the motor doesn't have a shorted winding?
  8. Alec_t

    Help with calculating Hz in a siren curcuit

    Not off-hand. Have you tried this calculator? It agrees with the LTspice simulation. Googling '555 timer formula' will answer your question.
  9. Alec_t

    Help with calculating Hz in a siren curcuit

    The frequencies are 0.36Hz and 327Hz to 1kHz according to LTspice.
  10. Alec_t

    Help with calculating Hz in a siren curcuit

    Putting those caps in series or in parallel is wrong. Check the schematic. Welcome to EP! Edit: Replacing the 1meg resistor with 270k will get you closer to 1Hz.
  11. Alec_t

    Current activated relay with timer

    Googling 'countdown timer switch' should find you something.
  12. Alec_t

    Automated Lighting project

    If your remote has 24 buttons it is almost certain that they are arranged in a scanned X-Y matrix, so applying logic 1 to a button contact is unlikely to work, whereas shorting two contacts will. Don't see how an Arduino alone could do that. Methinks relays would be needed. Directly sending IR...
  13. Alec_t

    Make one circuit current track with another circuit current

    Here's what I'd try, with the lamps connected in series to reduce the total current draw. When the lamps are on, there is about 6V across each (providing they are reasonably matched). The curves show the sharp turn-on motor current thresholds of the lamps for R1 values of 1Ω to 2.2Ω...
  14. Alec_t

    I need to power a synthesizer with a battery...Please Help :)

    If the USB hub needs an AC 110V supply, you can't use a car usb charger (12V DC to 5V DC converter) to power it.
  15. Alec_t

    Make one circuit current track with another circuit current

    Well, something simple like this could track the current over a limited range (0.3A to 0.6A in the sim) ..... but there would be a lot of wasted power in the transistor (up to ~3W)(blue curve) and R2 (up to ~7W)(red curve). Personally, I'd use on/off switching of the lamps instead.
  16. Alec_t

    Make one circuit current track with another circuit current

    Ok. What are the lamp's voltage and current spec for full brightness? (4V, 350mA I presume are less than the maximum rated values ?) I don't think you'll notice much ramping up and down in reality. Either the door motor will be off or drawing normal current (lamp off) or it will be stalled and...
  17. Alec_t

    Make one circuit current track with another circuit current

    Exactly so. I'm puzzled as to why you want to waste 350mA just to indicate that the coop door motor is taking excessive current? If you're really determined to do that, I can modify the circuit I posted.
  18. Alec_t

    I need to power a synthesizer with a battery...Please Help :)

    But what is its input voltage? If 12V, you're ready to go. If not, you'll need a DC/DC converter.
  19. Alec_t

    Operating a DMX controller with a footpedal - help and guidance please !

    Good to know it's all working.
  20. Alec_t

    Led sequence of 10

    You could get the up and down counting done with a bunch of logic ICs, but it would be rather messy. The obvious alternative would be a suitably programmed MCU (Arduino, PIC, what have you).
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