Search results

Search Forums New Posts
  1. Audioguru

    2 finger ECG circuit

    You never posted the schematic from cs.washington.edu. Maybe the schematic you posted is theirs or is it your copy? The bandpass filter is not bandpass, instead it is lowpass.
  2. Audioguru

    Use AC speakers in Car

    That is what small cheap speakers do. No bass, probably no highs and not much loudness. If your car battery is fully charged at 13.8V then the rectifiers will reduce it and feed about 12VDC to the circuit. But the 11.9VAC has a peak voltage of 1.414 times higher than 11.9V at 16.8V and the...
  3. Audioguru

    2 finger ECG circuit

    Look at my reply in the other forum about the common mode cancellation signal that is missing in your circuit and where the three probes should be connected on the patient. If you want to measure heartbeats on a finger then use an IR LED and IR detector that "sees" blood flow pulses.
  4. Audioguru

    LED Sequencer Help

    About 30 years ago I used opamps to make RGB sequencers like that. The colors faded and brightened slowly and randomly so the 3 colors were mixed randomly producing many colors including black and white.
  5. Audioguru

    Want to make an Electromyography amplifier circuit.

    N1 and N2 allow a pot to null any input offset voltage.
  6. Audioguru

    Power-One power supply mod

    Hevans, for 30VDC at 3A the output power is 90W but the AC from the transformer is about 119VA because the bridge rectifier heats with its voltage drop and the output transistors are powered from the rectified peak voltage of the 28VAC which is (28V x 1.414)= 39.6V - 2V (the drop from the bridge...
  7. Audioguru

    Want to make an Electromyography amplifier circuit.

    There is nothing called "input voltage compensation". Maybe you mean "Input Offset-Voltage Null" and its circuit is shown on the datasheet for the TL07x opamps. But a TL072 is a dual opamp without the offset voltage adjust pins that are on the TL071 single opamp. The null circuit is shown on the...
  8. Audioguru

    Want to make an Electromyography amplifier circuit.

    No. One diode is the rectifier and the important second diode prevents the output of the opamp from going as low as it can (almost -8V) on each negative half-cycle of the input signal. It takes time for the output of the opamp to swing back up to its normal operating voltage (causing a delay) so...
  9. Audioguru

    Astable Multivibrator Circuit (Flashing LEDs)

    It is a very simple transistor circuit. When you learn about transistors then you will see what each part does in the circuit and how to change the timing.
  10. Audioguru

    Power-One power supply mod

    Yes, the transformer you got is too puny.
  11. Audioguru

    Power-One power supply mod

    If you cannot phone the manufacturer to ask about the 120VA or 240VA rating then find a torroid transformer in a catalog online with the 240VA rating and compare its weight with the one you got.
  12. Audioguru

    Power-One power supply mod

    Yes, I think the heavy little bugger is too small to power two 120VA power supplies.
  13. Audioguru

    Want to make an Electromyography amplifier circuit.

    The output of your peak detector will swing negative as far as it can go on each negative half cycle of the input because then it has no negative feedback. This causes a delay for it to swing back up to normal operating voltage. The 2nd diode prevents it. The peak detector capacitor has no load...
  14. Audioguru

    Power-One power supply mod

    If both 28V secondaries of the new torroid transformer are in parallel then the maximum current from the power supply is 3A DC at 0V to 30VDC. Then each secondary can power its own power supply circuit and the currents will each be 1.5A max. I think the power rating of the transformer should be...
  15. Audioguru

    Want to make an Electromyography amplifier circuit.

    Did you learn anything about peak detectors?
  16. Audioguru

    Want to make an Electromyography amplifier circuit.

    The output of U4 will need attenuation so a high signal level does not destroy the input of the Arduino. How will you prevent negative voltages from the output of U4 from destroying the input of the Arduino?
  17. Audioguru

    Audio Amplifier Design

    Here we go again. I already answered and others too on electro-tech-online.com How many other websites will it be on??
  18. Audioguru

    Want to make an Electromyography amplifier circuit.

    Your INA106 still has a gain of 110 times, is that what you want? Times the 148 times gain of the output opamp= 16,280 times full of noise and interference. The datasheet for the INA106 shows the two opamps added to its inputs to make it an instrumentation amplifier with a high input impedance...
  19. Audioguru

    Light my lamps please!

    Maybe the AA cells were cheap Chinese "super heavy duty" garbage that died on the slow boat from China. New Energizer or Duracell alkaline cells last much longer. Will you randomly select the current rating for the wall wart?
  20. Audioguru

    Connecting a vintage microphone to a PC

    I am re-living my good old days because I am feeling younger every year I get older. After surviving a heart attack 8 years ago and watching the doctor put stents in my blocked heart arteries, I exercise much more, eat better and feel great. I also was blinded with cataracts (old age). I...
Top