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  1. (*steve*)

    Best Low-Cost Home PCB Prototyping?

    That's fine as long as your minimum feature size is 3mm. Do you mean 0.1mm? 1mm is horrible. Yes, PWM is used to vary the average power, however, as you reduce the power (even with PWM), the time it takes the laser to turn on changes. Semiconductor laser are far easier to control than CO2...
  2. (*steve*)

    Best Low-Cost Home PCB Prototyping?

    Laser cutting has the potential to be able to produce features far finer than milling. If your surface mount components include (say) sot-323, I'd be surprised if you could mill the board.
  3. (*steve*)

    Can anyone ID this transformer?

    The problem is that one can rectify the output of this transformer in multiple ways. To which configuration would the 60mA refer? I'm intending to full wage rectify the 500V to get approx 700V DC. The circuit it was in half wave rectified the secondary (with semiconductor diodes) and...
  4. (*steve*)

    Best Low-Cost Home PCB Prototyping?

    When I do pcb's on a laser cutter, I use a device with an 80W tube in it. It fits all your requirements except cost :-) Cheaper laser cutters might work. The device I use has way more power than I required and the management of the power is the largest part of the problem. I have a colleague...
  5. (*steve*)

    Can anyone ID this transformer?

    I have two of these transformers and I'm after some further information if anyone has anything. The high voltage secondary is marked as 250-0-250 and 60mA DC. There are three other secondary windings, 0-4-6.3 2A, 0-4-6.3 3A, and 0-4-5 3A. I'm curious about how to understand the rating...
  6. (*steve*)

    Car battery jumpstart gadgets

    I think we're getting waaaaay off topic.
  7. (*steve*)

    Replacement mosfet?

    Anything between the circuit benignly not working and smoke (with optional flames).
  8. (*steve*)

    Transistor Help!

    That's not 100% true. The device could be something that the tester can't test. Can you test for diode junctions between all combinations of pins. I.e. 1-2, 1-3, 2-1, 2-3, 3-1, and 3-2.
  9. (*steve*)

    Current measurement circuit

    I recommend you ask your teacher/lecturer/professor what sections you should brush up on so you understand the problems with loading of high impedance signals and how a voltage follower can improve things.
  10. (*steve*)

    Identifying transistor's PINs (Emitter and Collector)

    Yeah, there are numerous versions of them and they are amazingly versatile.
  11. (*steve*)

    Identifying transistor's PINs (Emitter and Collector)

    A transistor will display some transistor action with collector and emitter reversed. The gain will be much lower though. Generally you find a lower resistance between base and collector than you do between base and emitter. The reverse breakdown voltage for the base-emitter junction is less...
  12. (*steve*)

    Car battery jumpstart gadgets

    Not so long ago there was a whole stack of 3000F supercaps on eBay for less than $20 each. Apparently they were surplus after a failed project. They had screw terminals in the ends and from YouTube videos, were capable of huge currents. Not so cheap today. (Those ones are capable of 2200A...
  13. (*steve*)

    Car battery jumpstart gadgets

    Yeah, there are a number of supercap with very impressive current capability. And if you're not too concerned with maximum energy storage, very simple overvoltage protection can be used to stop charging once any cap reaches its maximum voltage. But again, the solution is a very low impedance...
  14. (*steve*)

    Car battery jumpstart gadgets

    Is there any good reason you couldn't make a switchmode power supply delivering (say) 200A from a standard 240V 10A outlet? I've seen computer power supplies that have power outputs in this range. Presumably they are protected similarly to smaller power supplies and might go into hicup mode if...
  15. (*steve*)

    Current measurement circuit

    What is your textbook? Perhaps someone here is familiar with it and can refer you to a section.
  16. (*steve*)

    g'day from skippy land

    Your multimeters may have fuses in them. It might be worth seeing if you can replace them. But do it after you understand how not to do it again in the future. What were you doing when you damaged your multimeters?
  17. (*steve*)

    Current measurement circuit

    Do you honestly think that if you tried to draw several hundred amps from a tiny battery that the voltage would increase? You need to go back to your lecturer and ask them what you need to read in your text to learn about this concept.
  18. (*steve*)

    Current measurement circuit

    What would happen to the voltage across a tiny battery if you tried to use it to start your car? The tiny battery has a high impedance.
  19. (*steve*)

    Current measurement circuit

    Imagine you have a 12Vcar battery and a 12V battery from a remote control (the ones about 2/3 the size of a AAA cell) You have to start a car, which one will work? Why won't the other one work? Can you apply this to the voltage signal from your circuit, with and without the voltage follower?
  20. (*steve*)

    Current measurement circuit

    You need to research that. It is something fundamental that you've missed somewhere. If you've been given this homework then you're expected to know this. Can you go back and check your notes?
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