Hobby Electronics Basics

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Transformerless power supply

Is it reasonable/possible to build an 8 amp 20 V transformerless power supply from a 120Vac line. I calculate about 180...
14 comments posted 7yrs
posted by nojunk
14 comments posted 7yrs posted by nojunk

Is Class 1 laser safe enough for baby eyes?

I meant, what if someone accidentally shine Class 1 laser into a baby's eyes? Would it hurt retina and leave a permanen...
3 comments posted 8yrs
posted by toylet.toylet
3 comments posted 8yrs posted by toylet.toylet

Formula for calculating run time of apc ?

I am looking for a formula for calculating the run time of my APC battery system. I did a search but what I found requi...
3 comments posted 8yrs
posted by andrewkennedy775
3 comments posted 8yrs posted by andrewkennedy775

An idea that may be of some use

I needed a small light to light some steps from my deck to the ground and in a few other places. I already had a 12V sy...
0 comments posted 8yrs
posted by default
0 comments posted 8yrs posted by default

three terminal volt regulator

Hi all, Simple question. Some 1/2 amp LM7805 is obselete (TO-220 pac) I need a replacement. So either a 1 amp 7805 http...
11 comments posted 8yrs
posted by gherold
11 comments posted 8yrs posted by gherold

mosfet bias question

I plan to use a mosfet in a dawn to dusk switching circuit with a 12V regulated power supply. In the application notes...
3 comments posted 8yrs
posted by default
3 comments posted 8yrs posted by default

juice the movie

http://juicethemovie.com/ Looks interesting. -- John Larkin Highland Technology, Inc lunatic fringe electronics
1 comments posted 8yrs
posted by jjlarkin
1 comments posted 8yrs posted by jjlarkin

Sanity check for a cheap DVM

I'd like to check an old Radio Shack DVM for accuracy around 5 volts DC. On a brand-new cr2032 coin cell it measures 3....
6 comments posted 8yrs
posted by bp
6 comments posted 8yrs posted by bp

Suppress transients on old burglar alarm

My 20 year old burglar alarm control has developed a fault that I've spent the last couple of days trying to fix. Befor...
15 comments posted 8yrs
posted by me
15 comments posted 8yrs posted by me

Capacitor Tester

I dont have a capacitor tester. (Well a very small one on my Digital meter) I want one that is good general use. Some s...
30 comments posted 8yrs
posted by stevwolf58
30 comments posted 8yrs posted by stevwolf58

current regulator

https://www.diodes.com/assets/Datasheets/AL5890.pdf The block diagram shows this as a closed-loop regulator, not just s...
14 comments posted 8yrs
posted by jjlarkin
14 comments posted 8yrs posted by jjlarkin

A balanced 12AX7 based buffer

I'd like to "design" and implement a simple 12AX7-based buffer for musical instrument DI purposes. I'd like the output...
7 comments posted 8yrs
posted by lcargill99
7 comments posted 8yrs posted by lcargill99

The wiper in a variac

I have been thinking about the way a variac works. One thing that puzzles me, is the wiper design: If the wiper is too...
7 comments posted 8yrs
posted by fake
7 comments posted 8yrs posted by fake

Trickle charge C-type NiMh?

I have some inexpensive 220 mAH C-type Ni-Mh batteries, https://www.amazon.co.uk/gp/product/B07BJ85NNZ The equivalent 3...
6 comments posted 8yrs
posted by me
6 comments posted 8yrs posted by me