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  1. BobK

    Cheapest way to get data from multiple(100s) of sensors?

    Multiplexers come in 8x1 typically, which means they can select 1 out of 8 analog inputs and send it to the output. Three inputs are used to tell it which one is selected. So you would have 50 chips to connect the 400 sensors, giving you 50 outputs. Then you would have 7 chips to select one...
  2. BobK

    Audio amplifier using a preamp and an lm386 audio ampl

    Are you talking about feedback from the speaker to the mic? If you remove the mic, does the "howling" stop? I would expect acoustic feedback with the mic that close the speaker if you have enough gain. Bob
  3. BobK

    Cheapest way to get data from multiple(100s) of sensors?

    You are going to need analog multiplexers to read the sensors. You cannot simply turn one of them on and wire them together for the reasons I have already stated. Bob
  4. BobK

    Light controller circuit

    Although it is hard to tell from that photo, it does not look burnt. Is the board operating normally? To measure it you would have to disconnect one lead then use an Ohmmeter. Do you know what it is supposed to be? Are there any marking on it or on the board that would indicate that, or do...
  5. BobK

    Light controller circuit

    It is most likely a power resistor, and it is expected to heat up, which is why it is spaced off the board for better airflow around it. Bob
  6. BobK

    Audio amplifier using a preamp and an lm386 audio ampl

    Where did you get that circuit? Just use the one on the LM386 datasheet. Bob
  7. BobK

    Effectively defeating PWM on Jeep Wrangler

    Hmm. I don't know how low / high beam is wired. Are there two connections to the LED headlight and two PWM outputs, or is the PWM signal itself changing from low to high? If the latter, you cannot use my solution, it would be on high beam always. Bob
  8. BobK

    Constant current (or voltage) source WITHOUT semiconductors?

    A battery makes a pretty good constant voltage source. Bob
  9. BobK

    Effectively defeating PWM on Jeep Wrangler

    Here is a circuit that might work. The capacitor needs to be determined experimetally, probably in the range of 100uF to several 1000 uF. The relay should be an automotive relay with a high enough current rating for the LED lights. Too small a capacitor would still flicker, too large a one...
  10. BobK

    Cheapest way to get data from multiple(100s) of sensors?

    You cannot get an analog output from the sensor without the resistor. Show us how you have it wired. Bob
  11. BobK

    Detecting Leveling of Arm and Shoulder

    I don't think there is a simple solution for this. In particular, one that only requires a device attached to the arm. Bob
  12. BobK

    Selection of presence sensor

    I think interrupting a beam would be the best solution. You need an IR source on one side and a detector on the other side. Depending on how wide the shower is, multiple ones are probably needed. Bob
  13. BobK

    Cheaper Source of Part#BT53

    Hi, and welcome to the forum. No one here is going to have a wholesale source of some random part. We would need to do the same searching you should be doing yourself. Bob
  14. BobK

    Cheapest way to get data from multiple(100s) of sensors?

    Did you look at my diagram? The ones that are off have a resistor connected to ground. That is 399 resistors connected to ground and 1 connected to V+, which reduces your signal by a factor of 400. Bob
  15. BobK

    How to test a capacitor

    There are many inexpensive component testers now available on Ebay. These will test resistors, capacitors, diodes, inductors and transistors. For capacitors they will give you the capacitance as well as ESR. Bob
  16. BobK

    Effectively defeating PWM on Jeep Wrangler

    The voltage might indeed vary from 8 to 12V, but that would not be PWM. Assuming the LED headlamps are intended to by powered by the 12V auto electrical system, I would use a relay to power the lights, and use the "PWM" signal to drive the relay coil through an RC low pass filter. Bob
  17. BobK

    Cheapest way to get data from multiple(100s) of sensors?

    If I understand you, your circuit looks like this: If so, there is a problem. The AN input will see 399 resistors to ground and 1 to V+, making the max voltage seen on the AN intput at V+ / 400. You might be able to make this work with a P channel MOSFET tying each R to V+ and the gate...
  18. BobK

    Using different inputs to access mp3 player's different tracks

    Sorry, but I cannot even imagine what you are trying to do with that circuit. It certainly does not allow you to select one of 4 clips on an MP3 player by pushing 1 of 4 buttons, which is what I thought you were trying to do. Bob
  19. BobK

    Li-ion charging circuit protector help

    It is not clear at all to me whether this interracts with a charger or includes the charger. Bob
  20. BobK

    Information for a complete beginner

    Urgent? Really? Well, I guess I am too late then, it has been over an hour since you posted. Bob
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