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  1. BobK

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

    Yes, you are missing something. In your circuit, every sensor in the selected column is connected together in parallel (i.e. all emitters and all collectors are connected together) With my modification they are not. Each emitter is connected to a row select. When the row select is high...
  2. BobK

    Why DC motor draws more current with friction?

    Current increases with voltage in a resistor. Other components are more complicated. The current of a running motor is determined by back EMF. The current in a stalled motor is determined by Ohm's law. Bob
  3. BobK

    Effectively defeating PWM on Jeep Wrangler

    No. It has no advantage over the relay circuit I offered. Meanwhile, you did not answer my questions. Bob
  4. BobK

    Differential Configuration for a Floating Signal

    What is the voltage between a floating voltage the ground of the instrument? Bob
  5. BobK

    LED driver

    You don't. It provides a constant current into any circuit that needs between 36 and 68V. So, if the sum of your forward voltages is 38V it should work just fine. Bob
  6. BobK

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

    My modification to your circuit requires fewer components. Read it again. Bob
  7. BobK

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

    Incandescants produce a lot of IR. So does the sun if there are windows in the room. I don't see why you are opposed to taking all of the sensors not activated out of the circuit. All you need to do is use a single collector resistor instead of multiple emitter resistors on each row. Now...
  8. BobK

    Laminator for PCB's ?

    They were both flexible enough to take the pcb thickness. They were just standard laminators, but the rubber rollers were flexible enough to admit it. The modification was to up the heat. The standard temp of laminators is not high enough for toner transfer. And to slow it down. I ran the...
  9. BobK

    How to slowdown capacitor discharge

    Charging capacitors is fast if you can supply a lot of power. In that video, there are 10 supercapacitors. If they are 1F each, then it is over 200000 times as much capacitance as your 47uF. I suspect that the capacitors were already charged when that video was taken, the few seconds of...
  10. BobK

    Connect Different Leds

    That MOSFET is way wrong. It requires 10V on the gate, which the Arduino cannot provide, and can handle 32A, when all you need is < 1A. What you need is a logic level N channel MOSFET that handles at least 1A of continuous current. The IRLD014, used in this thread...
  11. BobK

    How to slowdown capacitor discharge

    I hate to tell you this, but others have had the same idea. Some even think they can run an electric car off capacitors. They have been working on for about 10 years now, with nothing but missed deadlines and nothing to show (except a list of suckers who invested). Have a look at this...
  12. BobK

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

    That does not work either. Now you have all 20 sensors in parallel with a single emitter resistor. Sure, the IR led is not lit, but unless the room is dark, each sensor will conduct some current V+ to through that load resistor to ground based on the stray light hitting it. My method works...
  13. BobK

    Connect Different Leds

    To control brightness use a 5V supply, a resistor and PWM. You will need a MOSFET to turn the LED on an off with the PWM signal. Bob
  14. BobK

    How to slowdown capacitor discharge

    You would need a much larger capacitor, a supercapacitor, and it still would not be as size efficient as a battery. Why do want to run a motor off a capacitor? Rechargeable batteries are far more practical. Bob
  15. BobK

    equivalent for 2N4401

    2N3904 is also good. There are also BCxxx transistors that are more popular in Europe. Don't know what you have access to. Bob
  16. BobK

    Audio amplifier using a preamp and an lm386 audio ampl

    Why do you want a microphone within inches of the speaker? The way to eliminate acoustic feedback is to use a directional mike and point it away from the speaker. Putting the mic in a housing can make it more directional. Bob
  17. BobK

    Laminator for PCB's ?

    I have modified two different laminators to do this. It never worked very well. I have gone to pre-sensitized boards, with good results. So my advice, don't waste your time. Bob
  18. BobK

    How to slowdown capacitor discharge

    The energy stored in a capacitor is 1/2 C V^2. For your example: 47/1000000 * 235^2 / 2 = 1.3 Joules. 1 Joule is 1 Watt Second. An AA battery with a capacity of 2000mAH has 3W x 3600 seconds = 10800 Joules. Do you undersand why you cant run the motor very long off your capacitor now? Bob
  19. BobK

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

    Dorke, Here is the equivalent circuit when one of the 20 sensors in one of your columns is selected: The signal from the sensor has been reduced by a factor of 20. Though this might be workable, it certainly will not provide the same level of discrimination that the sensor is capable of...
  20. BobK

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

    Your solution does not handle multiplexing the outputs. Bob
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