Your best electronics troll - Page 1
Forum section: electronics / general

author: Unknown
author_rank: Unknown
timestamp: September 03, 2012, 08:36:38 pm
content: So, I was thinking about building a mains supply powered battery charger, but I was wondering what resistor I need to make the 240V go down to 1.5V? Are batteries even compatible with AC wattage?Here is what I calculated: 1.5V x 240V / 13 amps wattage = 27.69ohms resistor to make it down to 1.5V. Not sure if that's correct... It sounds a bit too low value.Also, do I need the Earth for my circuit? I can't figure out where it would go because my battery only has two ends on it and there's three pins on the socket. I want full protection from shorts.Thanks.

author: G7PSK
author_rank: Super Contributor
timestamp: September 03, 2012, 08:42:54 pm
content: I presume this post is in jest

author: tom66
author_rank: Super Contributor
timestamp: September 03, 2012, 09:26:31 pm
content: Why don't you just use a 7805 to step the mains down to 5V? Put two silicon diodes and one Schottky in series to get 1.5V.

author: Pack34
author_rank: Frequent Contributor
timestamp: September 03, 2012, 10:20:55 pm
content: Quote from: jim_griff on September 03, 2012, 09:38:57 pmOh, you....

author: tom66
author_rank: Super Contributor
timestamp: September 03, 2012, 10:22:19 pm
content: Only thing to be aware of using a 7500 ohm resistor is that is inductance may create a flux inductor resonance at 72/400 Hz (alternating at 6.5Hz.) Make sure to only use it in 50/60 Hz countries or in East Elbonia.

author: PbFoot
author_rank: Contributor
timestamp: September 04, 2012, 12:39:32 am
content: Well, when I worked as a network administrator, I told several users that they would get better network speed if they kept their ethernet cables smooth and free of kinks. You see, the zeros slip through just fine, but the edges of the ones can get caught up inside the cable.I also had purchasing order me a new box of tokens for the token ring network.-PbFoot

author: vk6zgo
author_rank: Super Contributor
timestamp: September 04, 2012, 02:36:12 am
content: Quote from: jim_griff on September 03, 2012, 08:36:38 pmHave you simulated it?

author: SeanB
author_rank: Super Contributor
timestamp: September 04, 2012, 04:50:16 am
content: The earth goes to the small potted Geranium next to the battery. This improves the charge retention, and the leaves are perfectly shaped so as to dissipate the spikes on the mains, leading to a richer fuller charge, with better quality retention, and a well rounded cycle on the battery.

author: Bored@Work
author_rank: Super Contributor
timestamp: September 04, 2012, 04:59:47 am
content: Quote from: SeanB on September 04, 2012, 04:50:16 amYou forgot to mention that it adds a warmth to the current stem.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 04, 2012, 08:06:32 am
content: Of course,you realise some dummy will actually build this thing,& sue you when he burns his house down,or electrocutes his cat?

author: vk6zgo
author_rank: Super Contributor
timestamp: September 04, 2012, 09:13:30 am
content: Sue their cat,too!

author: baljemmett
author_rank: Unknown
timestamp: September 04, 2012, 11:16:35 am
content: Quote from: jim_griff on September 04, 2012, 07:32:56 amJust be glad one of the knobs wasn't labelled 'SOAR'... (cf. day 23 ofThe Daily Adventures of Mixerman)

author: hans
author_rank: Super Contributor
timestamp: September 04, 2012, 11:21:23 am
content: You guys are making it way to complicated. Just use a resistor to connect to the battery, and make sure you have proper earth connection:

author: poorchava
author_rank: Super Contributor
timestamp: September 04, 2012, 11:45:45 am
content: QuoteIf someone would be that dumb, it's probably better for the society and overall gene pool of human race if that person indeed electrocutes itself to death.... or at least infertility. Now... let's think which nation is famous for placing most absurd warnings on everything and filing stupid lawsuits..."Putting this ceiling fan up your anus may cause discomfort"

author: free_electron
author_rank: Super Contributor
timestamp: September 04, 2012, 12:19:15 pm
content: As someone who hates calculations, here is how i would solve it :I go buy a relay , with a normally closed contact, and a coil that works at 1.5 volts.The coil goes to a bridge rectifier that itself gets the ac mains. The contact goes from ac to battery and the other side of the battery goes back to ac.Since the mains voltage is a sinewave that gose from zero to max , back to zero the relay will activate when it gets 1.5 volts. The comtact opens and the battery stops charging. When the sinewave has gone back to a value below 1.5 volts the relay will close again, resuming charging.Charging happens with a very high current but the duty cycle is very low so that should be ok. I don't expect the battery to heat up.Also , the incomi g ac voltage is not important. As the relay opens at 1.5 volts. This circuit works equally fine at 110 or 220 or even higher voltages.Additional bonus : it buzzes as an auditive feedback the circuit is plugged in and charging !

author: JamesAus
author_rank: Contributor
timestamp: September 04, 2012, 12:49:59 pm
content: Oh I like the earthing on that generator. A company I used to work for had a similar theory on earthing their Gentech genny's as well.....What you do is make a 500mm earth "T" bar out of stainless steel, that you can just push into the ground, clamp an earth wire to it and clamp the other end to the frame. It fell on deaf ears when several of us from the department told management that was a complete waste of time. Firstly the earth stake was totally inadequate, and the earth wire was connected to the frame that was isolated from the generator by rubber dampers. OH&S said we still had to use ELCBs with them when out on site though. I guess if it was raining at the time it had a slight chance of working??

author: JuKu
author_rank: Frequent Contributor
timestamp: September 04, 2012, 07:32:36 pm
content: A fellow was working on a pretty beefy power supply. He made all the checks and the again, but at one point, you just have to take the courage and plug it in. I was watching, with a piece of bubble wrap (the big bubble type) in my hand. I managed to make a "pop!" just in the right moment. The guy never trusted me again around his prototypes.

author: T4P
author_rank: Super Contributor
timestamp: September 04, 2012, 08:19:56 pm
content: Quote from: JuKu on September 04, 2012, 07:32:36 pmMMM, imma get some big bubble - bubble wrap and put it in my bag ... so when somebody plugs in something i know what to doPretty sure i got trolled by somebody or a failed PSUI was using some 3ch OHL PSU back at my college then i was wondering why my circuit wasn't working many hours later finally found out why :The Earth and Negative had been swapped ... (The colours were in the same position but internally it was different)No wonder i smelt smoke when i came back from the toiletLucky me wasn't the one testing

author: SeanB
author_rank: Super Contributor
timestamp: September 04, 2012, 08:21:54 pm
content: Steel ruler on table top, much beefier bang......................Even better was casually being near the door and turning the lights out at the appropriate moment.Best is the lift door, where there is a 2mm tolerance on the door closed and door fully closed safety interlock. Door closes but car will not move - safety circuit not closed. Leave for right length of time and then open door, the inside people walk out and are baffled why they are on same floor.............

author: T4P
author_rank: Super Contributor
timestamp: September 04, 2012, 08:33:18 pm
content: Quote from: SeanB on September 04, 2012, 08:21:54 pmWell, how do you do it?

author: G7PSK
author_rank: Super Contributor
timestamp: September 04, 2012, 08:40:43 pm
content: I once pulled a 13 amp plug fuse apart and replace the fuse wire with 500ma wire and black powder, I then put the fuse into the projector plug at college, It produced a rather bigger bang than I had anticipated and blew the plug out of the socket. It was put down to a faulty plug, needless to say I did not enlighten anybody.

author: SeanB
author_rank: Super Contributor
timestamp: September 04, 2012, 08:46:19 pm
content: Older lift with a swing door with lock, where you have to close the door fully before the car moves. Oldest lift I have seen near me is fully wood, including the latticework doors. Over a century old and still works, and complies to the required standards as well.