HarryA

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. https://www.amazon.com/Anmbest-Converter-Adjustable-Regulator-Protection/dp/B07R832BRX/ref=sr_1_41?crid=3ETDJKMX4K9ZO&dchild=1&keywords=dc+12v+converter+step+down+module&qid=1610919636&sprefix=dc+12v+step+down+converter+12v%2Caps%2C407&sr=8-41 I should get a kick-back from Amazon.com for all the times I reference them.😉

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:

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 controller that may work for you - rated 30 amperes. With luck you may get one that works - read the reviews. https://www.amazon.com/RioRand-7-80V-Motor-Controller-Switch/dp/B071NQ5G71/ref=sr_1_4?dchild=1&keywords=adjustable+voltage+regulator&qid=1610728630&sr=8-4 Now I see " it is a DC Motor Speed Controller,Not a Voltage Controller "

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 https://www.allaboutbirds.org/news/capturing-natural-sounds/

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 parts. https://www.ebay.com/itm/Stabilized-Continuous-Adjustable-DC-Regulated-Power-Supply-Kit-0-30V-2mA-3A-L/353345066780?hash=item524501d71c:g:JjsAAOSw~QteWLkt

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.

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. I could not find a Spice model for an avalanche diode so I used a low voltage zener for the BYV26E. Searching on "royer oscillator" brings up lots of hits. https://krishnamurthy1995.wordpress.com/2016/04/20/royer-oscillator-based-induction-heater/

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 wish to make sure that you are getting the results you expect by driving the circuit with a fixed frequency and seeing if you get any results at all. By the way there is an online signal generator that you can sweep your circuit with to find the resonance frequency and drive the pll for a first test perhaps. https://www.szynalski.com/tone-generator/ You can get the output through you pc's speaker output jack.

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 values. There are current detectors that encircle one lead that maybe less intrusive than a direct connection to the capacitor if you can find one that is sensitive enough.

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.

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 🤠

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: https://www.youtube.com/watch?v=oIE6bWj-lSU

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

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: https://www.ebay.com/itm/Rechargeable-Batteries-Li-ion-3-7V-Battery-Cell-For-Flashlight-Headlamp/133513298232?epid=27041280478&hash=item1f16034138:g:NGkAAOSwPSNfgRa4 Finding a charger that charges an odd number of cells is a challenge. There are slot chargers that charge cells in parallel that would be helpful if you can find one. The 11.1 batteries as used for radio control airplanes are expense and require balanced chargers. My IR animal detector uses a standard 9v battery that lasts for many weeks.

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 1k the current from Q2 would be limited to 33v/1k or 33ma well within the 88ma max. of U2. Else for the 0 or 22 ohms I would wonder about diode D10 if it is shorted or not.

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 dissipated, the circuit cools as desired. The shutdown circuit is then disengaged and the circuit heats up. Again shutdown occurs and so forth."

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

Q: Can the module amplify square wave or pulse? What is the module bandwidth? A: The module can amplify low-frequency square waves or pulses. Because it is an audio amplifier, the total bandwidth is not high. Signals within 100K can be amplified. The module is compatible with DC input. This is the over priced one with best Q/A https://www.amazon.com/operational-amplifier-current-continuous-voltage/dp/B07D8V1YBG/ref=sr_1_18?dchild=1&keywords=opa548&link_code=qs&qid=1605968887&sourceid=Mozilla-search&sr=8-18&tag=mozilla-20 The best price is 57.80$ Amazon.com - actually it's 35.60$ plus 5$ s/h on Ebay

The OPA548 op amp looks promising. It has up to 5 amperes output into 4 ohms or better. It can be bought in a complete amplifier see OPA348 on Ebay or Amazon.com just search for OPA548. The data sheet is here: https://www.ti.com/lit/ds/symlink/opa548.pdf As the amp can be used in a dc pwoer supply makes it look useful. If you have an Amazon account you can ask about the complete amplifier low frequency range else I can.

See the LM3886T at: https://www.alldatasheet.com/datasheet-pdf/pdf/8893/NSC/LM3886T.html?link=https%3A%2F%2Fwww.alldatasheet.com%2Fdatasheet-pdf%2Fpdf%2F8893%2FNSC%2FLM3886T.html It has a sample circuit with no capacitors in the pdf file. Also this amp board maybe useful, what ever "Pure DC Mono Power AMP Amplifier Board" means. It uses the LM3886T chip also: https://www.ebay.com/itm/LM3886T-x3-Parallel-150W-4-8-Assembly-Pure-DC-Mono-Power-AMP-Amplifier-Board/113895598886?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D225086%26meid%3D999c10d87a084a45a12ccb2f6e019c74%26pid%3D100005%26rk%3D2%26rkt%3D12%26mehot%3Dco%26sd%3D113918167015%26itm%3D113895598886%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv5PairwiseWebWithBBEV2bDemotionHighArwV3%26brand%3DUnbranded&_trksid=p2047675.c100005.m1851

I am not to sure what your question is. Are you asking can IC by its self, not in a package, be connected to a circuit on a PCB? Yes but it would need power and ground, etc connections also. An IC in a package like a DIP can. For example in the CDI (capacitor discharge ignition) circuit,that I am currently working on, the optoisolator (yellow) has the transistor directly connected to another device (MOSFET) on a another PCB.

Also sounding proofing outside going doors and windows with heavy fabric is said to help. Plus having sound absorbing rugs and wall hangs reduces the unwelcomed sounds. I see one cannot edit previous postings.

Some years ago there was research on noise suppression by picking up a noise and playing it back 180 degrees out of phase. If you played a sound through two speakers connected out of phase, that is so when one cone came out while the other went in, would they tend to cancel? Thus creating a small cone of silence.

My guess would be that D!! and C7 are to suppress superfluous outputs on at the power outputs. D10 is part of the biasing for Q2 transistor? Member audioguru is far more knowledgeable of this circuit than I; hopefully he will come by and give an expert input.

I see little or no difference using Firefox, Opera, or Edge. I am thinking that it is my monitor. Watching to many "Extra History" videos on YouTube.com is wearing out the pixels 📺 Thanks for trying.