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  1. (*steve*)

    More woes driving LEDs via PWM

    That MOSFET might work for you. The gate charge is pretty high, so you may need to consider this if you need to switch rapidly or at high frequency.
  2. (*steve*)

    PM 5192 ressurection

    He is a tip about carrying these units. Don't sling it under your arm and grip it by the lip at the back. The top cover is released by pulling it forward and up at the back of the unit. If the screws are firm but not right, carrying it this way will risk the top singing open and you...
  3. (*steve*)

    Solar powered plant waterer

    What you can do is to use the solar panel to charge a battery. When the battery voltage is above 13V turn the pump on, and then it off once the battery falls below 12V. A narrower voltage range will have the pump on more often but for a shorter time. This may be more suited to a hydroponic...
  4. (*steve*)

    What is this

    Or a fuse.
  5. (*steve*)

    PM 5192 ressurection

    I have a PM 5192 programmable synthesizer/function generator (0.1mHz - 20MHz). This is very similar to the PM 5193 except the latter goes all the way up to 50MHz. Mine is labeled as being a 100VAC unit, with a sticker saying 120VAC. Looking at the manual there is a different set of taps for...
  6. (*steve*)

    A Current Balance Circuit for LED Strings in Parallel with Polyswitch Protection

    It's even worse than that. LED efficiency decreases with increasing current, so all other things being equal, for the same average forward current a LED will have a slightly lower average brightness as the duty cycle decreases.
  7. (*steve*)

    What's this?

    Not really. It doesn't mean it was operated in a circuit with 1500V. The voltage rating of a capacitor is always higher than the voltage you expect to see across it. Maybe the voltage across it was only 800V and the designer thought that a 1000V cap did not have a sufficient margin for safety.
  8. (*steve*)

    A Current Balance Circuit for LED Strings in Parallel with Polyswitch Protection

    yeah, figure 3.5, but driving your string of LEDs. That's not a good way to go. One string may draw more current than the other if they are in parallel.
  9. (*steve*)

    A Current Balance Circuit for LED Strings in Parallel with Polyswitch Protection

    The LED resource is here. Section 3 is the part you're after. The circuits you've found are a reasonable source of the PWM to drive the constant current circuit. You probably don't want to drive the circuit I've given you at more than a few kHz and the choice of gate resistor is important to...
  10. (*steve*)

    14.8v @ 16 amps down to 12v @ 8 amps

    I would say "can cope with" rather than "require". edit: and depending on what you're talking about, even that may not be true.
  11. (*steve*)

    Transformer current rating

    There may not be a fuse there at all. It may be a recommendation. The designation suggests a non-resetable fuse.
  12. (*steve*)

    What's this?

    Possibly a 0.1uF 1500V capacitor. With your next few questions like this, why don't you have a guess too.
  13. (*steve*)

    A Current Balance Circuit for LED Strings in Parallel with Polyswitch Protection

    Can you quote figures that you've measured? I'm interested in the practical range of values that you have encountered. I have 1000 cheap LEDs from a no-name manufacturer that are not guaranteed to be from the same batch. Maybe I should check a few and see what sort of distribution I get and...
  14. (*steve*)

    Circuit Design

    A capacitor stores energy in an electric field. An inductor stores energy in a magnetic field. Inductors and capacitors are pretty much the reciprocal of each other. Whatever you know about voltage and current in capacitors you should understand as being about current and voltage in inductors...
  15. (*steve*)

    Circuit Design

    That is not a good question. It is a bit like a question where you close a switch and short a capacitor. If there is a resistor in parallel with the inductor in this case, the current will continue to flow through the inductor, reducing exponentially as the energy stored in its magnetic field...
  16. (*steve*)

    Solar powered plant waterer

    I would still use a pull even if the reservoir was at the top. This way you don't have to pump the water all the way up the stack of plants, just up and over the top of the container. The issue then is drainage and not watering too much. You either want to deliver based on measured wetness...
  17. (*steve*)

    Machines' "Parts Lists" (as opposed to a list of parts w/o ref to what machines they work in)?

    Ah you have started a thread. As I said elsewhere, any part can be used in any piece of equipment limited only by the designers imagination and any size/weight/cost constraints.
  18. (*steve*)

    Hello, Welcome! (Introduce yourself)

    Hi Marty. Welcome to electronics point. The book does not exist but could easily be written. Any part can be used in any device within the limits of the designers imagination and size/weight/cost constraints. If you want a better explanation, start a new thread :-)
  19. (*steve*)

    A Current Balance Circuit for LED Strings in Parallel with Polyswitch Protection

    I would select a MOSFET based on the current, max voltage, and max power dissipation. It is not particularly critical. Yes the zener is required to protect the gate when the supply voltage exceeds about 20V. The transistor is turned on by the current sense resistor which lowers the gate...
  20. (*steve*)

    A Current Balance Circuit for LED Strings in Parallel with Polyswitch Protection

    I would use something like this on each string, with the added protection of a 15V zener diode connected between the mosfet's gate and source. R1 is a value which will drop 0.6V at the rated current, and R2 can be between 10k and 100k. Q2 is any general purpose NPN transistor. Keeping each...
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