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  1. Alec_t

    Using Raspberry Pi to read signal generated by a function generator

    Make sure that the function generator signals are within the allowed input range of the ADC module. You may need a DC offset. Check the datasheets/specs of both the generator and the module.
  2. Alec_t

    Op Amp with a/c output

    Again, I've commented over at AAC.
  3. Alec_t

    Op Amp with a/c output

    I've commented on your frequency concern over at AAC.
  4. Alec_t

    Op Amp with a/c output

    If we take idle speed as, say, 600rpm then that's 10rps. The reluctor wheel would need 53 teeth to generate 530Hz at that speed. I believe wheels with 51 teeth or 40 teeth are common. Sounds like the Caddy's is a 51 teeth type, or could be a 40 teeth one with a higher idle speed. My circuit was...
  5. Alec_t

    Op Amp with a/c output

    Here's a simpler circuit which amplifies a sine input from a sensor at terminals 1,2. The output at S,V, is a similar shape with a peak-to-peak voltage clamped at 12V (the assumed supply voltage). Note that the voltage difference between S and V has both negative and positive peaks. The polarity...
  6. Alec_t

    Op Amp with a/c output

    Try replacing D3 with a 100uF >=25V-rated capacitor, cap negative terminal connected to Q1 collector.
  7. Alec_t

    Considerations to make this contraption work ?

    With that set-up the LED will be on while C charges up to 2.5V, then goes off. C continues to charge, since Rd provides positive feedback. There ain't no sharkfin :(. Personally, I'd probably use a CD4093B as a 1Hz oscillator, gated by the dark sensor.
  8. Alec_t

    Replace old transformer with rectifier bridge

    If you value your life, or the lives of others, DON'T USE IT!! It has no mains isolation, so anything powered by it could float at mains potential and be LETHAL.
  9. Alec_t

    Replace old transformer with rectifier bridge

    That board apparently already has a bridge rectifier (4 diodes) on it. A transformer is a completely different animal. If the one you show has failed you will need to replace it with a similarly (or more generously) rated one, or a suitably rated wall-wart (mains to low DC voltage adapter)...
  10. Alec_t

    Snap action night light...

    This might suit your complementary MOSFET IC if its FETs are logic-level types with low turn-on threshold voltages : R1 value depends on the photodiode sensitivity. R3 provides hysteresis feedback. Either could be replaced by a trimmer for set-up.
  11. Alec_t

    Shutter Glasses

    In the interests of safety, make sure that any user of these glasses does not suffer from epilepsy. Sudden light brightness variations at frequencies in that range are known to trigger epileptic seizures in susceptible people.
  12. Alec_t

    Can't find CR2032 3V rechargeables, safe to use 3.6V LIR2032?

    Here's the basis for a primitive volt-dropper. The first plot shows variation of the output voltage for a fixed 100uA load current as the cell voltage drops from 3.8V to 3.2V. The second plot shows variation of the output voltage for a fixed 3.7V cell voltage as load current is ramped from 0 to...
  13. Alec_t

    Pulse dropping circuit.

    Here's the modified circuit. The main change is back-to-back zeners across Q1,Q2 to avoid base-emitter breakdown if the supply voltage is >9V. I also increased various time constants to cope better with lower input pulse frequencies than the original circuit was designed for.
  14. Alec_t

    Pulse dropping circuit.

    Sorry, I was checking the wrong nodes. Good catch. With a 12V supply I see ~6.3 Veb. With a 9V supply ~4.8 Veb. I'll work on a modification.
  15. Alec_t

    Help with power supply

    Comparable cameras advertised seem to draw current in the 50mA-200mA range, so a small 12V SLA battery would do the job. However, given the seller's warning about over-volting the camera I'd be tempted to use a voltage regulator to take the camera volts down to, say, 9V.
  16. Alec_t

    Help with power supply

    Welcome to EP! According to those specs a 12V supply would suit both devices. How much current does the camera require?
  17. Alec_t

    Pulse dropping circuit.

    0.6V, regardless of supply voltage Vdd. Q1 and Q2 protect each other, being wired in inverse-parallel. Edit: Running the sim again I see that the two time-constants R(pot)C5 and R5C2 will need tweaking depending on the pulse frequency range to be covered.
  18. Alec_t

    Pulse dropping circuit.

    LTspice says 'yes', even a bigger range, providing the fixed pulse-width is appropriate for the input frequency range considered, i.e. is less than the minimum input pulse period. Here's the .asc if you want to play.
  19. Alec_t

    Got any ideas for using an old fridge?

    Repair it? Use it as a proving oven if you make your own bread? Re-orientate it if necessary and fit it with shelves to store your electronis stuff? Convert to novelty bath-tub? Dog kennel?
  20. Alec_t

    Pulse dropping circuit.

    Here's my design which can be used to raise or lower a pulse frequency, with a simple pot adjustment. Setting the pot at 60% of its travel should give you the required 2/3 lower pulse frequency. U1 is a hex inverter. U1a,U1b,R1,R2 are configured as a Schmitt trigger inverter. Q1,Q2 ,Q3 provide...
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