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  1. J

    Help with simple circuit

    How are you measuring amps? Not parallel to the resistor I hope. I don't know but 2.5 amps is 2500mA which is what most cells are rated at. BTW, you measure current in SERIES only.
  2. J

    Illuminated 'Push Button' Help

    Say hello to the arduino, it has a wifi shield and ethernet shield. There is even a simple data logger plugin that you could buy if you could always download the data.log later on. Here is the link to the datalogger. http://www.ladyada.net/make/logshield/
  3. J

    suggest any title for fresher party

    I am pretty sure this is probably off topic
  4. J

    Solar Help

    Lithium ion cells probably aren't the best to use in this case. You have to make sure the temperature of the batteries during charging doesn't go above about 45C. They make special IC's just for the purpose of charging lithium ion cells. If you heat a lithium ion battery up too much, like...
  5. J

    Question regarding pass transistors

    I have this transformer, it is a transformer out of a car battery charger with a 50A start setting. It also has a winding for 6V. Seeing as how the output is center tapped and I have a primary winding for 6V wouldn't that suggest the transformer has a +12 to -12 output? I haven't tried to...
  6. J

    Question regarding pass transistors

    I didn't see a graph in the LM317 stating that with increased voltage difference current drops off. Is this supposed to be assumed or is it just the reality of how a VR works? I haven't really read a lot of datahseets and haven't had to much real world experience with components, just mostly...
  7. J

    Question regarding pass transistors

    You have given me a good idea. I have a 18V laptop power supply that must be SMPS as with no load it has almost zero voltage output. You won't get that with a linear supply. Is this what you mean and then use this output to drive a linear voltage regulator of say 12V? Would you mind...
  8. J

    Question regarding pass transistors

    1 Ohm To build a supply that I can use on the bench. Doesn't have any specific purpose, But I would like to have a usable supply with the typical voltages up to 12 or 24 depending on what would be easier with at least 5A of current, since I think this should cover most things I plan on trying...
  9. J

    Batteries vs. Power Supplies

    as long as it is 12V dc you shouldn't see any issues. Only issue would be if the voltage was unregulated and varied a lot, then the possible current would be greater then the LED could handle and they would be junk.
  10. J

    Question regarding pass transistors

    Ok, so let me know what won't work here. I have calculated the values 1.5A llm 4A Ice I have also calculated my transistor power dissipation to be 95W when the output voltage is 3.3V. Is this correct and can the 2955 even handle this? I guess now the question is what size heat-sink I will...
  11. J

    Question regarding pass transistors

    ok, so after looking at the specs I realize a high power PSU is out of the question with a select-able output voltage. Given that I think this should cope with all that I want. How does this look??? Only thing I don't get it what the value of R8 should be, if I understand the equation then a...
  12. J

    tacho

    I would assume the chips is bad too. Do you only have two of the same chips? Is there a test circuit in the datasheet that you could use to test the IC?
  13. J

    Suppressor Advice Needed

    I don't know, but a zener regulates voltage pretty well. Though I am no expert, so better let someone else ring in.
  14. J

    Question regarding pass transistors

    Now that I look at it this way, Would I be better off to use a VR for every voltage I want and then use a rotary switch to select the VR and incorporate a 1 resistor per VR to turn on 1 pass transistor? Edit: I will try and draw a schematic of the above in case my description is poor.
  15. J

    Question regarding pass transistors

    So let me see if I understand this. If I was to use a 30V input and design for worse case current max, then I would need to take my input 30V and subtract my lowest output voltage 3.3V to get my biggest in/out differential. That is equal to ~26V @ 2A. This would mean that my 2955 wouldn't even...
  16. J

    Question regarding pass transistors

    What is llm and Ube stand for? I don't understand sry I have drawn a schematic of what I think would be the correct way to build a variable PSU. I want this to be a select-able PSU with say a rotary Switch, so I can have say 3.3, 5, 9, 12, 24V output. I will redraw the schematic with a rotary...
  17. J

    Using 2 wall warts for + and - supply

    couldn't you just cut one of the grounds and all would work ok? I mean if they are hooked in series then wouldn't the ground for one PSU work for both?
  18. J

    temp control iron

    I have actually seen quite a few people do this on the net and post pictures of a light dimmer switch and a electrical outlet all contained in a electrical box. I had plans on doing this since I have some ancient solder irons. The real big ones with wood handles and braided electrical cords...
  19. J

    Solar Help

    The way this is going to work is you will charge the batteries and then run everything off the batteries. Takes to much effort to switch from one to the other, besides batteries where designed to handle this type of use. Secondly, you can't shut off the power being provided by the solar cells...
  20. J

    weird question... i think

    Better re-read what advice was given. It is a good way to short your amplifier and ruin it. That is a little more then nothing. You should have said, "Nothing good!"
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