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  1. HarryA1

    Rheostat power rating

    I believe you are correct. Yes they are beefy - see: https://www.ebay.com/itm/OHMITE-RHEOSTAT-100-OHMS-100-WATT-MODEL-K-STOCK-NO-0451/223494235238?hash=item34094b6466:g:MHYAAOSwJHhcwbwy You could consider using a 1 ampere fast blow fuse.  Ideally one could put a second power mosfet at the...
  2. HarryA1

    SMD code "MFN", "=AG-"

     The codes most likely only have meaning to the manufacture of the circuit board they are on.  Manufactures do not want customers to be able to repair their products rather them buy new ones. Can you find a schematic?
  3. HarryA1

    PWM-PSU Voltage Adjustment

    Bear in mind the headroom for the LM388 is 3 volts. The headroom voltage refers to the actual voltage drop across the regulator that must occur during operation. So that means that the most you can get out of the above circuit is 9 volts. Minus the drop across the 0.3 ohm resistor. You maybe...
  4. HarryA1

    PWM-PSU Voltage Adjustment

    The max for the LM388 is 12 amperes: Look at the the Buck Converter  here; one reviewer is pushing it to 25 amperes with a fan/blower cooling...
  5. HarryA1

    PWM-PSU Voltage Adjustment

    You do  not need the bridge diode nor the 4700 mfd capacitor but keep the 0.1 mfd as it is typically in voltage regulators of that type.  You may need heat sinks and heat sink compound; look up "lm388 pdf" files for more information. This illustration is set up for 5 volts:
  6. HarryA1

    PWM-PSU Voltage Adjustment

    It may work but as you say it is not  very efficient. You can stack voltage regulators to get the current you need if you wish to roll our own. See the 4-20 volt 20 ampere circuit here: https://www.eleccircuit.com/high-power-supply-regulater-0-30v-20a-by-lm338/ Also you can buy a motor...
  7. HarryA1

    Parabolic Mic choices

    There is a good write-up here that maybe helpfu- using the Knowles Electronics, Inc. EK23029 electret condenser microphone: http://oldbird.org/mike_home.htm Also see: https://en.wikipedia.org/wiki/Microphone#Application-specific_designs and...
  8. HarryA1

    0-30V Stabilized Power Supply

    The best you can do is to start at the  output transistors and work your way back through the circuit. It is impossible to diagnose homemade circuits at a distance as there are just to many places to go wrong. For others never build something you can buy cheaper. Get two at 8$ each - one for...
  9. HarryA1

    Big zap really fast

    To Calculate C when Vf, R, t and Vi are known; see https://hoven-in.appspot.com/Home/Blog/rc-discharge-calculator.html For R = 4 (0.004k) ohms, Vstart = 400v, Vend = 300v, and time = 15ms I got C = 13035 μF.
  10. HarryA1

    Detecting Resonance in an Electrolysis System

    Also consider  power oscillators. Like the royer oscillator used in induction furnaces. Your capacitor would be part of the oscillator circuit thus solves the resonance problem. I tried one in LTspice like the one in this link; got oscillations similar to your voltage and current display above...
  11. HarryA1

    Detecting Resonance in an Electrolysis System

    I would think that the transformer would destroy the nature of the resonance circuit. Are you thinking that if you find the resonance frequency of the real circuit then as the water is consumed it would change the resonance frequency by the change in capacity of the cell/capacitor?  You may...
  12. HarryA1

    Detecting Resonance in an Electrolysis System

    I believe the only way one may detect resonance is with something that has a memory be it human or microcomputer. One  needs to know that it is passing resonance peak and then backup. A microcomputer could store values and keep comparing the values until the current value is less then previous...
  13. HarryA1

    0-30V Stabilized Power Supply

    If the spikes are only there while rotating the potentiometer then it is a bad pot. If they are there in cc mode always then you can trace them back through the op amps output to inputs until you narrow down the source.
  14. HarryA1

    0-30V Stabilized Power Supply

    You need to post the schematic you are working from. Perhaps start a new thread with a similar title? A fresh start is always a good start  🤠
  15. HarryA1

    Need some help powering motion detector water spray

    Your cells should charge up to 4v or so; I would think them to be okay. The BMS board is for charging. There are cells with protection built-in but they are expensive. There are simple devices you may add to a cell for such protection: Here is a video on single cell protection...
  16. HarryA1

    Need help in project development

    What controller? What/which NTC temperature sensor? Are you asking how to acquire the data from the sensor into the controller?
  17. HarryA1

    Need some help powering motion detector water spray

    You could use three 3.7v cells to make up a 11.1/12v battery. For example  three 9800 mAh would be; 9.8 Ah * 11.1 or 108.78 Watt hours. The valve only use 4.8 watts and the standby current for the IR unit is only 50 microAmps. For example...
  18. HarryA1

    0-30V 0-3A Latest Data

    There are others who are more qualified than I on this circuit but not letting ignorance stand in my way I will continue anyway. In the various schematics U2 is connected to a transistor base through a 0, 22, or 1k ohm resistor. So it makes a difference which schematics you are referring to. At...
  19. HarryA1

    hyland 0-30v psu output osillates

    At 3 seconds pulsing you could see that with a multimeter. I would start at the output of U2 looking for pulses; if so look at its input and likewise back to U1 and U2 outputs and inputs. The op amps U1 - U3 (TL081) are short circuit protected. "When shutdown occurs and less power is...
  20. HarryA1

    hyland 0-30v psu output osillates

    Do you have a better schematic? It's hard to read this one. Can you reference where you got the schematic or the kit?
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