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  1. Alec_t

    555 timer to turn on 2nd 555 timer

    You have pin 2 going to LED1 (correct), but also to 2 other things (wrong). Pins 3 and 4 seem to be shorted together? Pins 4 and 5 don't seem to be connected to D2 and R5?
  2. Alec_t

    555 timer to turn on 2nd 555 timer

    That info should help the diagnosis. How long did you wait for the red LED to come on? I see you now have 100k in place of the SetDelay pot. That will increase the delay to about 11 sec.
  3. Alec_t

    8 channel sinusoidal function generator

    How will you achieve the focussing? Transducers ususally radiate with a divergent beam. To get a reasonable sinewave you are going to need, say, twenty samples per cycle per transducer. So the MCU would have to spit out samples at 20MHz x 8 = 160MHz. On top of that you would need processing...
  4. Alec_t

    555 timer to turn on 2nd 555 timer

    The detailed notes are very helpful. The BC547 will be fine. Can you post the pin numbers you used for the inputs/outputs of the gates that I identified as U1a to U1f in the latest schematic? If pin 1 is the input to U1a then something seems miswired if its voltage doesn't rise above 1.8V...
  5. Alec_t

    8 channel sinusoidal function generator

    Welcome to EP! 15Vpp into 50 Ohms is about 0.5W. So you would be supplying ~4W total electrical energy, which seems on the low side for levitiating any significant load. What would you be using as the medium for levitation? I suspect air transducers at 1MHz would be very inefficient for your...
  6. Alec_t

    555 timer to turn on 2nd 555 timer

    Good luck with the build. Take particular note of diode orientation and the way the 40106 is wired in the latest version. Since now only three gates (d,e,f) are paralleled it is not advisable to drive a LED from their output. LED current causes a voltage drop across the internal resistance of...
  7. Alec_t

    math problem, I lost my marbles it seems

    Unfortunately no. Have another try.
  8. Alec_t

    Diode with One Volt cut in voltage

    Don't know about Orcad, but in LTspice a crude model can be as simple as .model mydiode d(vfwd=1)
  9. Alec_t

    math problem, I lost my marbles it seems

    Re-arrange the formula :- B =R2*(1/R1 + 1) mod edit: deleted full solution. From here on it'S up to the op to show us he understands and can contine on his own feet.
  10. Alec_t

    555 timer to turn on 2nd 555 timer

    Oops. Wrong schematic, and I should have said C1 discharges via R4. This is the one I intended :
  11. Alec_t

    Clean 20Mhz square wave at 45 volts ... possible???

    Many function generators are intended for driving low current loads only. As Bluejets says, a dedicated FET driver may help, since it is designed to handle high current needed to charge/discharge the gate capacitance quickly.
  12. Alec_t

    555 timer to turn on 2nd 555 timer

    Here's an improved circuit, to cater for the fact that not all gates within the CD40106 IC may have exactly the same trip threshold voltages (due to manufacturing tolerances, or if there were a severe temperature gradient across the IC chip). Note the different connections of the gates U1b to...
  13. Alec_t

    555 timer to turn on 2nd 555 timer

    Here's a modification of the circuit. It now works in a somewhat different way. At power-up Q1 turns on and the oscillator starts immediately, generating narrow pulses to drive the servo fully CCW. After the delay, Q1 turns off, so the oscillator generates wide pulses to drive the servo fully...
  14. Alec_t

    555 timer to turn on 2nd 555 timer

    Good to know. I'll have a think re the CCW reset. Watch this space.
  15. Alec_t

    555 timer to turn on 2nd 555 timer

    Driving a red LED, as well as the servo control signal input, from the paralleled CMOS outputs may pull the pin 8 voltage too low for reliable servo operation. You could try driving that LED from pin 2 instead, but this would need the LED plus current-limiting resistor to be connected between...
  16. Alec_t

    555 timer to turn on 2nd 555 timer

    To make up 220n you need to put your 100n, 100n, 20n in parallel (not series). As presently arranged, the combined capacitance is <20n, so the pulse timing is way off and the servo won't respond correctly (if at all). Pin 8 is intended to be held low for the duration of the delay, so 0.7V as...
  17. Alec_t

    Circuit validation & improvement

    You could use a PWM buck regulator, as AG suggested in post #8.
  18. Alec_t

    Hopefully simple question about mobile phone motherboard.

    Why? That's probably why you now have a poor connection :(.
  19. Alec_t

    Circuit validation & improvement

    Well, unless the battery cells themselves dissipate the power it has to be disspiated by Q1 (be that a MJ11028 or a MOSFET).
  20. Alec_t

    Circuit validation & improvement

    Just wondering, how big a heatsink do you have for Q1? Dropping ~10V at 80A means you have to dissipate ~800W as heat somewhere :eek:.
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