Recent content by Pyramid

  1. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    I built up the circuit using 5V, a CD4093 and a high brightness (2500 mcd) Red LED. Using a 330Ω resistor swamped the gate and it wouldn't toggle. Increasing the LED resistor to 1K allowed it to operate and it had plenty of brightness. If you need more brightness, then use a PNP transistor...
  2. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    The opamps and the 74HC132 are still powered from the 5V VCC so it should work. Even at 3mA, most high brightness LEDs will work fine in this circuit.
  3. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    The thresholds are 11V / 10V / 9.5V, so post #3. The 74HC132 is a replacement for a CD4093, but with higher drive capability. Check that the pin out is the same (I don't have a data sheet in front of me). Find a Piezo beeper that runs from 5V and is self exciting (when you supply 5V, it...
  4. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    The circuit does not monitor individual cells. It measures the total input voltage, but the thesholds are fixed by the resistors between 5V and ground. The opamps work as voltage comparators. They are comparing the (divided down x2.8) input voltage from the battery to a fixed reference...
  5. Pyramid

    How to find RPM of motor using KY-040 Rotary Decoder Encoder

    You will need to count the pulses from the encoder over a fixed period of time. If I recall correctly, the KY-040 produces 20 pulses per revolution, so assuming the encoder shaft is directly connected to the motor shaft, and you count pulses for 1 second, then RPM= count/20 * 60 = count*3...
  6. Pyramid

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

    MeanWell LRS-150F-12 159 x 97 x 30mm.
  7. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    I just realized you may be able to simplify the circuit by gating the flasher and beeper oscillators directly: The 4093 has 4 gates in one package, so you would only need 1 chip.
  8. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    U1A/B/C is an op amp with rail to rail inputs (the input voltage range includes the supply voltage and ground). You will need at least the positive rail input i.e. a TL064 type op amp. Op amps are high gain, high input impedance, low output impedance, differential amplifiers that can be...
  9. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    J1 is the input from the battery stack. I assume you wanted to power the circuit from the batteries? The ground connection would also be to the battery minus. Vcc is the supply to the opamp (pin 4) and the 4093 chips (pin 14) which both run off 5VDC.
  10. Pyramid

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    Maybe something like this: R11 and R12 scale the voltages by 2.8x so you can power the opamp by 5VDC (same with the 4093 logic). The opamp will need to be a rail-to-rail input type. The LED should be a 3 lead device for simplicity. The buzzer should be a self exciting piezo buzzer for...
  11. Pyramid

    Book Reviews

    OK, I have some questions about writing a book and getting it published: I recently retired from my company that I started in 1990; we designed and manufactured high end communications equipment for public safety and military applications. I wrote all of the operating systems in 8051...
  12. Pyramid

    What the latch?

    Please see post #11 above. If I read the OP correctly, he wanted a simple set/reset type flip-flop which this circuit provides. It may be simpler to use a octal latch i.e. 74273 types, but they don't have individual sets/resets. The 74 series has higher current variants (AC), but they are...
  13. Pyramid

    What the latch?

    74 series chips will almost all be TTL levels so limited to 5V supplies. You could try this 4000 series CMOS equivalent to the 7414: http://www.digikey.com/product-detail/en/texas-instruments/CD40106BEE4/296-36082-5-ND/1690637 It is pin compatible to the 7414 and can drive 3-4mA directly...
  14. Pyramid

    What the latch?

    How about something like this: 7414 chips are ~0.50 and you get 3 circuits per chip. You can have individual set switches and one reset switch for the whole group if you isolate them with a diode.
  15. Pyramid

    Resistor on illuminated switch but without dimming the circuit LEDs??

    If you're blowing up LEDs with a 9V battery, I'm guessing the switch does not include the dropping resistor. One of the reasons they don't include the resistor is that you can tailor the switch to the voltage it will be used with (the resistor will change depending on the supply voltage, per...
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