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  1. KrisBlueNZ

    Need help with 555 timer circuit

    Hmm. Thanks for the feedback. I'll have to reconsider my recommendation for that device, if it's going to prove difficult to work with. I wouldn't worry about overheating the device. If you're worried, you could solder it like this: 1. Stick the leads through the stripboard. 2. Tin a lead...
  2. KrisBlueNZ

    PopularAltering a LED Flasher Circuit? - Will it support MANY LEDs???

    Flashing multiple LEDs This diagram shows a general way to flash a large number of LEDs in unison. On the left is the power source. It is shown as a battery but would normally be a power supply, since the LEDs can draw quite a lot of current. The ideal voltage is 12V. Do not exceed 15V...
  3. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    Yes, but the fault may not be the microcontroller itself - it's more likely to be a fault affecting one of the signals that the microcontroller is monitoring. If the microcontrollers aren't socketed, you should install sockets so they will be from now on.
  4. KrisBlueNZ

    Comparator for anemometer

    To increase the input impedance of the circuit. The hysteresis is determined by the ratio between the feedback resistor (from output to non-inverting input) to the resistance between the non-inverting input and the reference point (the voltage divider). With the original arrangement, the...
  5. KrisBlueNZ

    Comparator for anemometer

    OK, the OPA2244 looks good. I assume you're still using a 5V supply? I've updated my design for the higher output impedance of the anemometer, and adjusted the bias resistors to suit the OPA2244. I've also added Cin which may help reduce false triggering due to noise coupled into the cable...
  6. KrisBlueNZ

    Looking for a simple circuit design...really

    Yes. The "0V" connection connects to the negative of the battery supply (which is the vehicle chassis, I assume), and the screen of the audio cable that goes to the headphone socket. The centre wire of the audio cable, which goes to the "tip" of the headphone plug, is the "IN" signal.
  7. KrisBlueNZ

    Mosfet driver IR2104 High out not working

    No, that's fine. You don't need a load on the MOSFETs. Just make sure the rest of the circuit is fully connected up. If the 12V supply is going into current limit, the driver IC may be damaged. If it's in an IC socket, remove it and see whether the overload disappears. If the overload...
  8. KrisBlueNZ

    2222a simple question

    The traditional way to make an LED blink is the two-transistor astable multivibrator. See http://www.reprise.com/host/circuits/transistor_flasher.asp. There are two diagrams there; the left hand one uses NPN transistors and is the usual one. It says that the supply voltage range is 5~12V but...
  9. KrisBlueNZ

    Need help with 555 timer circuit

    Here's a circuit description. I've used some jargon here; if there's any terminology or concept you don't understand, look it up on Wikipedia, or Google it. The circuit uses two CD4093B quad NAND Schmitt trigger ICs. Each IC contains four NAND gates. Each gate has two inputs and an output. If...
  10. KrisBlueNZ

    Looking for a simple circuit design...really

    The voltage and current available from a headphone jack are quite low. You will not be able to power an LED directly from it, nor activate a relay with it. You need an amplification stage to increase the audio level, and a signal detector to convert the AC into a clean on/off signal to drive the...
  11. KrisBlueNZ

    Need help with 555 timer circuit

    Here's a method that MAY work: cross-couple pin 4 of IC3/4 to pin 2 of the other IC with a 1k~10k series resistor. Disconnect pin 4 of IC3 and IC4 from your positive rail. Connect a resistor (1k~10k, doesn't matter) from IC3 pin 4 to IC4 pin 2. Connect a resistor (ditto) from IC4 pin 4 to IC3...
  12. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    Thanks for that nice explicit picture. As I thought, the relays are both being driven to the wrong states. The control signals are wrong. These signals come from one or both of the microcontrollers. The east end of R29 currently has 5V; this should be 0V. The nnorth end of the resistor closest...
  13. KrisBlueNZ

    help with oscillator driving comparator

    When you added a buffer, what problem did you have? Did adding the buffer cause distortion at the output of the oscillator at high frequencies, or did the buffer work OK until you connected the comparator to it? The LM7171 isn't a comparator; it's an op-amp - specifically a "voltage feedback"...
  14. KrisBlueNZ

    Mosfet driver IR2104 High out not working

    OK. VCC=12V and diode=1N4007 is fine. For operation at 50 Hz, the bootstrap capacitor should be about 1 uF. I recommend a 50V X7R ceramic capacitor like http://www.digikey.com/product-detail/en/C3216X7R1H105K160AB/445-1423-1-ND/569089 (surface-mount) or...
  15. KrisBlueNZ

    Mosfet driver IR2104 High out not working

    Hi Sophie and welcome to Electronics Point :-) As Bob says, the most likely reason for the top MOSFET not turning on is a problem with the bootstrap voltage on the VB pin (pin 8). As long as you are driving the device with a pulse signal at about 1 kHz or higher, with a duty cycle between say...
  16. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    OK. It seems that both of those relays are in the path from the mains input to the heater, and both of them are in the opposite state from what they need to be to operate the heater. The outer (west-most) relay needs to be energised to activate the heater. In that state, there would be 0V on...
  17. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    Right. And there are no connections on the top side to the six other holes on each relay.
  18. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    Sorry, I was just talking about the six holes at the south end of each relay. There are no tracks to them on the top side, are there? Can you answer those other questions?
  19. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    I'm not sure I understand. First, can you confirm there are no tracks running to the relays on the top side of the PCB. Second, are there any part number markings on the relays? Thirdly: Connect your voltmeter black lead to the 7805 heatsink tab. Connect the red lead to the stripe end of...
  20. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    That's odd. It looks like there are NO tracks going to the relay terminals on the top side. Is that right? If that's right, then both of those relays control the heater, and I can't see any reason why there are two of them. Have you measured the voltages on the four north end pins of the relays?
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