Everything for Electronics

Unanswered Questions





Battery Woes 2020 Issue-4

I have some brand new lead-acid batteries that have never been used. They have been stored in my garage for a while (1-1/2 to 2 yrs). My smart charger errors and won’t charge them. Why is this and is there anything that can be done to revive them?

#04205
Reva Pino
Charlotte, NC


Capacitor P&Cs 2020 Issue-4

What are the pros and cons for using electrolytic capacitors in a voltage divider circuit to provide about 24 volts AC to a heater cable from the 120 volt AC line?

Is there a possibility of having a capacitor explode from overheating? If so, could that be prevented by stringing several capacitors in parallel to provide for additional heat dissipation?

#04204
Robert Gotts
Madison, IN


Temperature Sensing LEDs 2020 Issue-4

I’m looking for a temperature sensing circuit that will light each of three LEDs at approximately 80°F, 90°F, and 100°F.

#04203
Matthew Seltzer
via Internet


Fan Indicator 2020 Issue-4

Good day to all you experts!  I have a plywood basement floor that is suspended like any other floor in the house (bentonite soil in my area requires this construction). The actual dirt ground is about two feet below the wood floor, covered by a rubber tarp.

To prevent a build-up of mold and stale air, this space has a 6” duct vent fan that turns on via a humidity sensor rheostat. The supply side duct is on one side of my basement and the evacuation duct is on the other.

In the past, I could hear this fan running, so I knew when the bearings were wearing out. It was an easy job to buy a new duct fan and replace it. We just had our basement finished, putting drywall around the perimeter wall. Now I can no longer hear this fan when it kicks on.

Does anybody have a suggestion for some sort of sensor that detects when the fan is turned on by the humidity sensor but drawing too large of a current supply, so on the verge of bearing failure? Ideally, I would like some sort of an indicator light that I can make part of the access panel that is over the fan. Even an AC ammeter movement would be adequate.

At the location of the fan, I have both the switched 120 VAC power supply and a constant 120 VAC available if needed. I don’t have the specifications on this exact fan available, but a quick search online found several that had operating currents of 0.35-0.40 amps. I know the start-up amps would be a little higher but not too much because the motor is small and has very little inertia to overcome. Thank you for any suggestions!

#04202
Bill Young
Denver, CO


Component Footprints 2020 Issue-4

Can someone please explain the standards for the footprint of electronic components? I’m trying to figure out the the best way to lay things out on a circuit board. I’m new at this and any advice would be appreciated.

#04201
James Devera
Scandinavia, WI


Electronic Candle Circuit 2020 Issue-3

I’m looking for a simple circuit for a 24 hour electronic candle that uses very little power. The candle would drive a single LED. It would run for x hours (say five), then turn off; 24 hours after it  has first activated, it would automatically turn back on for the predefined time.

I've found several ideas, but most of them surrounded the 555 chip which has a very limited time frame.

#03205
Scott Lapp
Simi Valley, CA


Home Circuit Boards 2020 Issue-3

Does anyone still make oneoff circuit boards at home? What methods are being used by hobbyists and where do you get supplies?

#03204
Alvaro Collazo
Gulfport, MS


Transformer 2020 Issue-3

How do I calculate the number of turns for both the primary and the secondary windings of a transformer?

#0323
Opeyemi
Ibadan, Oyo


Model Train Controller 2020 Issue-3

My son has recently become a model train enthusiast and asked me how to control multiple trains on the same track. Is it possible and how would one go about building a controller?

#0322
Paul Sills
Grand Rapids, MI


Amplifier For VHF TV 2020 Issue-3

I have a rather complicated TV reception system. I have four antennas all successfully combined into one by using modules to convert the RF signal to VHF siganls. What I am lacking is a constant input for all signals into the combiner.

I would like to take signals from 54-216 MHz with 1-8 dBmV input and put out 18-25 dBmV with as little noise as possible. It would be great if I could clamp all signals to 25 dBmV.

#03201
Howard Epstein
Gilford, NH

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