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Recent content by yougarage

  1. Y

    trigger on peak in AC waveform

    Hi, I just made some tests. I tested with a BC547 NPN I had laying around. The two pics refers to different capacitor values (based on the schematic 3 posts ago). I found that a 103 cap produces ringing, probably the base current is too high. I then tested a 102 cap, and works fine. I also...
  2. Y

    trigger on peak in AC waveform

    I know the peak is a bad place to trigger, but I'm stuck with this. This is a capacitive discharge ignition unit from a small engine. The magneto output this signal only, it is used for both charging the capacitor and for timing. The low spike at the top of the wave is probably noise induced by...
  3. Y

    trigger on peak in AC waveform

    Thanks for your suggestions. The generator accelerate and decelerate fast, so I cannot use betwixt's solution. The signal is from a flywheel-magneto of a engine. this is the circuit suggested by chuckey. Would you go for a Darlington transistor? Should I limit the base current in some way?
  4. Y

    trigger on peak in AC waveform

    Hi! I need to trigger an interrupt in a microcontroller when a AC signal reaches the top peak value. The AC signal I'm talking about, vary in frequency (20 - 200 Hz) and voltage (500 - 1000 V). It comes from a generator, when it turns faster, the frequency and the voltage raise. I thought of a...
  5. Y

    selecting the right transformer

    Hi, I'm going to build a power supply project I found on Digikey : http://www.powerint.com/sites/default/files/PDFFiles/der58.pdf I'm having problem about the transformer selection. On the pdf, it is explained how to build it, but I' d like to buy a ready made one. Coud you point me in the right...
  6. Y

    scr gate resistor choice

    You are right, the gate trigger voltage is 0.6 v typical, 1.5 max
  7. Y

    scr gate resistor choice

    Hi! I need to drive a SCR with a microcontroller, so I' figuring out which gate resistor to use. The scr is a BT151, the datasheet shows a typical gate trigger current of 2mA to 15mA max. The microcontroller has 50 mA push pull capability. Based on these data, a 220 ohm resistor should give...
  8. Y

    catching pulse below ground

    Thanks for your replies both solutions look interesting, however the first avoid a current load to the sensor, right?
  9. Y

    catching pulse below ground

    Hi, I have a variable reluctance sensor(a pick up) monitoring a half moon wheel.One wire of the sensor is grounded. It's output is a positive pulse when the pickup meet the full edge of the wheel, and a negative pulse when it meets the other edge. I need to pick these signals to feed a mcu, I...
  10. Y

    simple digital amplifier

    Hi, I have a digital signal coming out from a IC, it has a square wave shape, and the IC has an open collector output, so the output line is pulled up by a 10k resistor to + 5v. Because this signal has to travel for about 2 meters in a harsh environment before reaching the microcontroller, I'd...
  11. Y

    series resistors on lcd data lines

    Thanks for your advices I'm using all the 8 bit data lines so I won't have unused pins.
  12. Y

    series resistors on lcd data lines

    Hi! I'm designing a simple pcb to interface a microcontroller to a parallel graphic lcd.(HD44780 standard) I'm wondering if I would need to put series resistors between the data lines and the microcontroller. I tested it without them, it works fine, but I'd like to improve reliability and noise...
  13. Y

    Question about autoprotection feature in mosfet

    Hello! I'm using a mosfet from SGS-THOMSON, the VND5N07 to switch a lamp with pwm. I drive it with a 4 Amps mosfet driver, the MCP14E3. A 22 Ohm resistor is placed between the driver and the mosfet. This mosfet has the feature of being autoprotected, when the threshold temperature is reached...
  14. Y

    How to add reverse polarity connection protection to a power mosfet circuit

    Hi! I'm designing a simple power mosfet circuit to interface a MCU to a 12 volts system. The schematic is attached, I'd like to have a suggestion if any improvement could be made, in particular I'd need to add a reverse polarity connection protection. How could this be achieved? I tought to add...
  15. Y

    high voltage triac circuit

    Thanks for posting this picture, but I don't want to make an electronic ignition, I just want to interrupt a working one, let's say i need to interpose the switch between the generator and the ignition coil I modified the previous picture so I can show you.
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