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Hung Chang HC-2020 multimeter repair, I would check the divider string for a failed resistor R7 or short-circuit maybe on the rotary switch. You'll need another multimeter to check the parts inside. It's a strange problem though.
Schematic: https://elektrotanya.com/hc_2020.jpg/download.html#dl
Why do you worry so much about stability before it's built? Do you need sub % voltage regulation?
I evaluate this on the bench as simulations are interesting but frequently out to lunch.
As you know 1uF MLCC is nowhere near 1uF in practice. The inductor plays a large role in filtering EMC...
It's actually underthinking.
Answer one question -
What are the consequences of the insulation failing?
1. Fire, house burns down.
2. A little smoke, fuse pops.
3. Granny gets electrocuted.
3. Nothing because it won't happen, the official numbers are "way too large".
In your snubber, or...
"Sorry, the download link that you are looking for is either expired or invalid."
I thought a flipped diode would basically short the output. The 47Ω resistor burning up would be a bad (open E-B junction) power transistor when the PSU has a heavy load on it. I would recheck the schematic and...
Using a 3A fuse, the aux battery terminal voltage will be forced up quickly and a partially discharged 4.5Ah SLA charging current does fall back quickly as well. We dont know if the load has a low voltage disconnect, my dashcam I have it set at 12.2V so I can at least start the car. Will the aux...
I wasn't sure what OP means with 'disconnected':
"keep the tracker with power all the time and make sure that if main battery is disconnected the rest of the car wont take power from the backup battery, (i only want the backup battery to power the tracker only)."
It seems to be in the context...
The mystery component is not a varistor/MOV. It is PTC thermistor, polyfuse X185 50V which holds 1.85A, similar to a Littelfuse RXEF185.
You have the 1N4001 diode backwards. Band/cathode should connect to the output, not to GND.
Also missing are 1-2 other protection diodes used when charging...
Short-haul CAN within a product you can get away with a lot, it depends on speed and length of the stub. Is the bias split and termination done at least on the other end?
If you're doing a PC board design, just leave a provision for termination resistors and a "do not populate" directive. Then...
This is what I had in mind.
The car's main battery is always connected to the trickle charger. The ideal diode prevents the backup battery from ever powering the car electronics, during cranking, remote door locks etc.
A smart charger needs to see a battery at all times. If the car battery was...
Welcome to the forum :)
OK your sketch has everything wired in parallel - which doesn't work as you want but I get the idea.
It's the same need for RV's, motorhomes, caravans - a dual battery system, but only one powers the car.
What you want is an "ideal diode" module feeding the backup...
PNP yes- it's an open-feedback loop, over-voltage shutdown. The TOP2xx "V" pin has multiple functions.
If the feedback loop went wonky, the aux winding's high output voltage say >14.6V here would turn on the PNP and inject current to the "V" pin which forces the IC to go into latching shutdown...
Never let the "customer" dictate a safety component, such as a fuse. That is for you, the responsible member to specify- unless you are not liable in your work per your contract. Even then, you have a professional ethics obligation to not make unsafe product. Congratulations on saving pennies...
5x3W metal film resistors for inrush on a 4,300uF cap??? That's hilarious. As a big spender, you'll need to spend more than pennies in the 4kW league. Your power supply project will not succeed with that mindset, prepare for exploding resistors.
The LT spice sim gave peak power over 1.1kW each...
It might be overheating if the Magnastat switch is stuck on. Blue tips are when it's quite hot.
When you operate it with no tip, there should be no heat. When you put the tip in, you should hear and feel the "click" from the magnet closing the Magnastat switch contacts. Could also use an...
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