Search results

Search Forums New Posts
  1. KrisBlueNZ

    Light dimming circuit

    OK, so you changed the working voltage from 230VAC to 12VAC without changing any of the components, and your simulation program didn't have the proper DIAC so you chose one at random. Is there anything else you should have mentioned? SCRs and triacs are not well suited to low voltage...
  2. KrisBlueNZ

    Tektronix 465 scope issues

    It might be helpful if you posted a schematic with measured voltages marked (set the position controls to mid-position).
  3. KrisBlueNZ

    Heavy duty fixed frequency radiant charger project

    It's OK, we have nothing to fear from this invention. He's using a transformer from a microwave oven. The spark is only a few millimetres long. He doesn't seem to have discovered that electricity doesn't acquire its magical properties until the spark is at least two inches long. And there is no...
  4. KrisBlueNZ

    LDR circuit.. no luck :(

    Thanks Steve. Feel free to start from scratch with the design. You might find it simpler to hack the LDR into the existing circuitry and sacrifice the low battery cutoff feature.
  5. KrisBlueNZ

    Light dimming circuit

    You're running a triac-based light dimmer at 12VAC. Did you take a mains design and just reduce the input voltage? Also, what is the part number of D2? I get no hits for "1N5758" on Digikey and Mouser.
  6. KrisBlueNZ

    Heavy duty fixed frequency radiant charger project

    Awww, Steve, I wanted to see the overunity device / EMP generator / water deioniser / fuel efficiency product / whatever it was! And I think I have a spare thronomister or two in the shed, along with my NOS flux capacitors.
  7. KrisBlueNZ

    LDR circuit.. no luck :(

    Maybe. There must be someone in your school who does electronics as a hobby... Could you put a note on a notice board somewhere?
  8. KrisBlueNZ

    LDR circuit.. no luck :(

    I wouldn't ask the staff at an electronic components shop. It's not their job to teach you how to build stuff. Can you find someone else at your school to help? You'll really need someone who can spend a bit of time on the project. BTW there's a mistake in that earlier schematic - the...
  9. KrisBlueNZ

    LDR circuit.. no luck :(

    OK here's a schematic of the board that's in there, and the circuitry you need to add. The new components are shown in the bottom part of the drawing. As you see, you'll need a few transistors, some resistors, and two trimmer potentiometers. VR1 sets the darkness detection threshold, and VR2...
  10. KrisBlueNZ

    LDR circuit.. no luck :(

    Thanks for that information. I'll upload a schematic soon. Are you sure that all the transistors have the same marking? I would expect one of them to be different. Could you check please?
  11. KrisBlueNZ

    Problem with Heathkit IO-102 oscilloscope - vertical deflection doesn't change

    I guess the prime suspects are the JFETs, Q1 and maybe Q3. JFETs can be easily damaged by high voltages. What is the part number? It looks like EL131. Google EL131 JFET, there are lots of hits including someone who was looking for a replacement for his Heathkit scope. I've never heard of EL131...
  12. KrisBlueNZ

    Relay driver

    It is possible to make a circuit that will switch a relay based on a signal that swings from 0V to +0.5V but I doubt that's the proper voltage. There is no reason for a microcontroller that's running at 1.5~4.5V to generate an output of only 0.5V, unless it has been damaged or is generating a...
  13. KrisBlueNZ

    Electronics

    If you want to know where you can buy electronic components, tell us what country you're in (there's a place in your profile for that information) and someone may know.
  14. KrisBlueNZ

    What value of resistors do I need and a sanity check

    OK thanks for that. I don't think it'll tell us anything though. The simulator says there's 1.93V across the LED and zener, and there's 1.93 uA leakage current through the zener. I doubt that current is accurate. The simulator may just be assuming a 1 megohm leakage resistance at that voltage...
  15. KrisBlueNZ

    LDR circuit.. no luck :(

    It seems that the circuitry on the board is just there to prevent over-discharge of the battery. When the battery voltage drops too low, the lamp is turned off. Once you give me the component markings I'll be able to confirm that this is the only function of the circuitry on the PCB. It will be...
  16. KrisBlueNZ

    Does this dc - dc booster have regulated Vout?

    That buck-boost converter looks good.
  17. KrisBlueNZ

    LDR circuit.. no luck :(

    That's very helpful. Can you give the markings for each component? The transistors are the most important, but anything with letters or numbers marked on it is significant, and the coloured bands on each of the resistors would help too. As I suspected, there's no charge control circuit. The...
  18. KrisBlueNZ

    LDR circuit.. no luck :(

    Thanks for the pictures! Can you check that I understand this properly. The circuit board has the following connections. 1. A jack socket, for the wire from the solar panel. 2. A small connector that goes to the three-cell battery pack. 3. Two wires that go to the light. 4. A red and black pair...
  19. KrisBlueNZ

    LDR circuit.. no luck :(

    Yes, if you post some pictures I should be able to tell you what to connect to where. You'll need a light-operated relay. Google those keywords. It's a circuit that monitors the light level using an LDR, and drives a relay that can be set to open and close at specific light levels. This relay...
  20. KrisBlueNZ

    What value of resistors do I need and a sanity check

    That looks good, Bobby. Regarding DZ. Can you tell from the simulation, how much current is flowing in DZ? If it's less than around 100 uA it should be OK to leave it there, but if it passes too much current, it will affect the base voltage, which is supposed to be determined by the LED only...
Top