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  1. HarryA1

    Current drop relay for coffee grinder auto off

    I gather you are looking for a circuit like this one. Do you have any idea what the currents are? Perhaps one could key off the change in voltage at the battery; low voltage turns a transistor on to  power a relay. Edited: The circuit needs a momentarily open push button switch  between the...
  2. HarryA1

    Rheostat power rating

    There is something about pulse transformers dealing with the pulse width. If the input pulse width is two short the current never has time to build up completely do to the lagging current in an inductor/coil. That would look like an impedance mismatch also. If the pulse is to wide current is...
  3. HarryA1

    Camera 6v power supply

    Yes you can use a battery as long as it is 6.0 volts. How long it will last will depend on how much  current the camera draws. If you are using 4 AA batteries there is good information here:  https://www.powerstream.com/AA-tests.htm
  4. HarryA1

    Rheostat power rating

    Your getting  just 3 volts suggest an impedance mismatch between the transformer and the cell.  In looking at using automobile ignition coils for high voltage I see a number of videos and articles where they get huge sparks from the coils that I can not get. I feel like you; where is the spark...
  5. HarryA1

    Rheostat power rating

    We know the output voltage is related to the ratio of the number of turns. And the output current related to the inverse of the number of turns. The more voltage gives one more current at the primary so in an ideal transformer the power is the same on both sides of the transformer. But in a...
  6. HarryA1

    Rheostat power rating

    Using the 100 watt bulb and two different ignition coils this is what I got: AC Output(VOM) 1 meg load        Input sig. 204 Hz   Peak voltage  across 7ohms      coil type 67.4 v                                             6.0v                          1.84  v                                ...
  7. HarryA1

    Rheostat power rating

    Don't laugh that is an emulation of your circuit. I was thinking that there is not enough load in the circuit with only the coil (the mosfets are acting like switches only off or on) so I started out with 7 watt incandescent lamps but could not get two mosfet to work so I switched to only one...
  8. HarryA1

    Rheostat power rating

    I was using the fixed resistors as the simulator dos not have a concept of a potentiometer. Putting the 530 back in an using a combination of two resistors  between 30k - 17k to 46k -  1k (where the lower value is to ground) I get good results with 40k - 7k  and 30k - 17k but the peak current is...
  9. HarryA1

    Rheostat power rating

    I would think you are not hitting it with enough current. Using a resistor instead of the IRF530 as it is faster to use rather then dorking around with two resistors to simulate a pot. I am using a input pulses that 2.5 ms  on and 2.5 ms off at 6.8 volts peak No bifilar coil nor diode in the...
  10. HarryA1

    Desing a regulated voltage source with a transistor and a zener

    New section: For R1(max). Assuming a 8 volt transformer. Vin = 8.0  * 1.4 or 11.2 Taking the min and max to be plus or minus 10%. One would not need a voltage regulator if there where nothing to regulate.   Vmin = (Vin - 10%*Vin) - (2 * voltage drop across the two diodes). Typically 0.7v...
  11. HarryA1

    Desing a regulated voltage source with a transistor and a zener

    Part one: Starting on the right: the load resistor minimum would be Ro = Vout/Iout. As the transistor is used as an emitter follower the output will be near a voltage gain of one. For the Zener diode and Vout of 6.0v you must allow for the voltage drop Vbe (Vb to Ve) of 0.6 to 0.7 volts.  So...
  12. HarryA1

    Rheostat power rating

    In the simulator (with 100 ohms between the PSU and the coil and 1 ohm resistor in the source lead of the ITF840) the output is about 1.2kv peak with or without the 1.164 meg  resistor. With the 1.058nF capacitor it drops to about 750v and with the 5.18nF it drops to about 450v. The current...
  13. HarryA1

    Rheostat power rating

    Can you measure the resistance of the cell? Possible it got comtaminated. Also knowing the size of the electrodes and their separation  in water one could get a first order  approximation of the cell's capacitance.
  14. HarryA1

    0-30 V PSU negative supply not working

    I must admit the more I look at the circuit the more confused I get. Why the negative rail connects to the TL081 is beyond me. Why it connects to the 30 v rail when it is only rated 18v max is a mystery to me also. Also there are many different up grades to the circuit I gather; for example I...
  15. HarryA1

    Rheostat power rating

    What happens when you connect the load? You may try to connect a small capacitor across the output if you have one that has the  required voltage rating. The last trace maybe as good as you can get. I will try adding distributed capacitance to the windings to see if that produces similar results...
  16. HarryA1

    0-30 V PSU negative supply not working

    Putting just the front  end into the simulator. The labels in large print map back to the schematic. Using a 4.7 volt zener simulator doesn't have a 5.1 zener.   In these traces the green is the voltage on the negative rail and the yellow is between D6 and R3.   In this one the green trace...
  17. HarryA1

    Filter Cores question

    What is a Nilma Radio?  Are these band pass filters used in the antenna input used when selection one of two radio bands?  If you have both types of inductor cores why not use them? As you are on the upper limit of the T37-2 cores and the T37-6 cores (lower limit) do not need to go below the...
  18. HarryA1

    Rheostat power rating

    As a first try  the circuit below  has a transformer with the primary of 1.8mh and 0.1 ohm while the secondary is 720mh and 150 ohms. The inductance is related to the number of turns squared ratio: 25^2 to 500^2 =  625/250000 =    0.0025 thus ( 0.0025  *  720mh) = 1.8mh  So your guess is a lot...
  19. HarryA1

    Light font?

    I set the browser to display the links in large bold fonts. As the first page is all links that did what I wanted to do.
  20. HarryA1

    Rheostat power rating

    What are you using for input pulses? Any idea what the inductance of the primary and secondary windings of the transformer are? Else does anyone have a good guess what they may be? I have never used inductors enough to get any concept of what  transformer inductance like that would be. I can...
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