Best products from r/Electricity

a) If you want to be able to run the three of them at full speed, you need a > 120W power supply (12V3.3A3 = 118.8W) that outputs either fixed 12 V or variable voltage that covers some of the range 0-12. This should be relatively easy to find in a hardware or a circuits store. You could even possibly use a computer PSU with some hacks, assuming the different output support this wattage at 12V.

b) I wouldn't think so. I'm not an electrician but I believe many simple dimmers are mostly inductors or have some internal circuitry to drop the voltage, most of them assuming AC in and AC out which is not your case. You want a DC-DC converter, ideally this is internal to the power supply itself (variable output power supply), there are also relatively simple circuits that do this (look switch mode power supplies, dc/dc converters), or you can go with a simpler (but lossier) solution with an in-series resistors or a number of diodes (ca 0.7-1V drop each), just note that those will simply "burn off" excess voltage, and combined with the amperage you are giving they will produce quite a lot of heat (you'll need high wattage components and heatsinks). Another solution here is a low frequency pulse width modulator (PWM) that alternates between pulses of 12V and 0V, though depending on the internals of the fan this may or may not work.

c) Again the answer here is it depends on the type of fan. So motors like you'll find in fans need some sort of an oscillating circuit to get the fan moving, it's not a simple resistive circuit, if it were, you're assumption about the linear relationship between voltage and current is correct. Most of these fans are designed in such a way as to reduce their speed with lower input voltage, but the exact relationship between voltage, current and the fan RPM is likely nonlinear and fan dependent. Most computer fans for example have 3 pin connectors, with the one pin giving a pulse on each fan rotation (I believe) which is how the motherboard can see how fast it is rotating. This is a form of a feedback mechanism which can be used by a driver circuit to figure out what voltage output is needed to reduce the fan rotation to a certain point (you want a certain RPM, you lower the voltage until you get it).

To summarize, you are probably best off getting a variable voltage power supply, something like this: https://www.amazon.com/Yescom-Precision-Variable-Digital-Adjustable/dp/B00SWK6M0M (note I have no idea about the quality of this model). You can then wire up all the fans in parallel and change the voltage to change the fan speed. Make sure you don't output much more than 12V as you will likely destroy the fans. If you are looking for a more permanent solution you can find some variable power supplies that fit your needs and are less "user interfacy" and more robust to sit and run for extended times.

A bonus of the bench top power supply is that it will be super handy when you start messing around with circuits in general. To understand more I recommend picking up the basics of circuit analysis, e.g. https://www.khanacademy.org/science/electrical-engineering/ee-circuit-analysis-topic (I have not gone through this myself), going to your nearest hardware store, get a breadboard and some components and start playing around.

Nah I just wanted to make a point when someone on a thread said it uses a lot of electricity. I know a USB 1.0 doesn't use much more than a wireless mouse!

You know sometimes as a female who did not study science I may not know exactly how much electricity but i know for sure a USB 1.0 device does not use a "shitton" of electricity!

1c a day is less than a Starbucks a year. 😛

Just standing up for myself. Troll alert plus they exaggerate myths to prey on people's insecurities! I do not like that. I use science and despite not studying any science, I come pretty close to a solution. Proud of my self 😊

Any idea how much electricity a 6 can refrigerator will take? Example this one on Amazon?

I am really keen keen to get one. The 1 can solution failed. It only cools the bottom 😑

The two power supplies as far as the peltiers 'see' is the same thing as having one big one. I do think it may prove to be simpler wiring this way though, as you don't really want to mess with a bigger gauge wire than 8. I agree 8-10 is fine for this, I wouldn't go smaller. Make sure everything is fused.

Just think about what happens if the peltier gets too hot, would be good to have a way to trip the system and prevent things from going bad fast. The good news is thermal switches are not that expensive
edit: I think these are all normally-closed, you can select the temp you need. Make sure to analyze whether you need a normally-closed or normally-open switch for how you want to trip your system.

these ones are only rated for 5A, would be nice to have a few in paralell that could trip the whole unit off at a certian level - if it was a computer power supply you could use a bunch of normally-closed ones in series and use that on the pin that allows the PSU to turn on. Can also have one for each peltier and they can turn themselves on and off dynamically.

From my experience, these small batteries are pretty well useless. If you need battery power to make it through the day since you are a heavy user. I suggest getting something like this. I have had good success. Battery

I'm an engineer at an electric utility and we use Snap Circuits to demonstrate basic concepts of electricity to middle- and high-schoolers. The kit has a lot of variety in the activities and is a simple means of experimenting with electricity. It's easy to assemble and reconfigure too, which is nice. I've spent hours at various public outreach events playing with this toy and would recommend it to kids and adults alike.

> higher the output wattage the more expensive they get so this would only be suitable for relatively low power devices.

When I moved to England ~1983, I bought three 1.5 kilowatt step downs to run my items. Including a waffle iron I loved. I found them used but even new they are not that much. You should only need one of that size for things like heating appliances. 250 Watt one are fine for most computer/audio/video use.

Look to Amazon or Ebay. And the safest ones are real transformers. Not the switch mode ones suitable only for heaters.

I think I understand. The amount of watts won't power too many items, nor for too long either.

How about something like these, they look to be a lot more powerful.

https://www.amazon.com/dp/B01MA4YVNP/ref=sspa_dk_detail_4?psc=1&pd_rd_i=B01MA4YVNP&pd_rd_wg=gcDdU&pd_rd_r=Z3AWGKAGPANFREC3D84E&pd_rd_w=Rd1Wx

https://www.amazon.com/dp/B06ZZNMV1Z?aaxitk=uV7TMys1GViwLYfYEhwPLg&pd_rd_i=B06ZZNMV1Z&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=5582544217303223519&pf_rd_s=desktop-sx-top-slot&pf_rd_t=301&pf_rd_i=single+phase+generator+power+supply&hsa_cr_id=2323616880101


Thanks for your response. Power/electricity is something that I don't understand particularly well.

Its an inline probably 6.3 mm crimp (the one in the picture has probably been machine crimped but you can use these

https://www.amazon.co.uk/insulated-Female-terminals-connectors-Delivery/dp/B00A3VETO4/ref=sr_1_7?s=diy&ie=UTF8&qid=1482250808&sr=1-7&keywords=terminal+crimps

They are pretty easily obtained especially for car stereo stuff
You can also get a male to go into this female unit

Something like this??

https://www.amazon.com/GEREE-Waterproof-Converter-Module-Double/dp/B00NGJO55S/ref=sr_1_9?ie=UTF8&qid=1487263184&sr=8-9&keywords=buck+boost+converter+5v

Your comment was very helpful.

Now for the size of the motor, I imagine a giant motor that was geared to turn slowly would lose a lot of power in the inefficiency of the motor, but too small of a motor, and it would probably over heat.
Should I be looking at motors based on Watts? Volts?

What prevents the generator from turning into a motor, powered by my cell phone battery? Do I need a diode or something?

Please excuse my electrical ignorance, and thanks again

there’s a fuse box under the hood as well if that’s a better option. if you go for the interior fuse box, you can probably tuck the cord into the weather stripping on the door to get it out of the way. these are also really handy for keeping things neat

So you mean if you don't physically touch them, they are safer than the good ol' christmas lights? Because I see too many people complaining. Could it be a placebo?

I thought about something like this

I’d s try an smart strip first before bringing in an electrician to solve the problem. See if that solves your issue first.

Maybe something like this: Smart Strip LCG-3MVR Energy Saving Surge Protector with Autoswitching Technology, 10-Outlet https://www.amazon.com/dp/B0006PUDQK/ref=cm_sw_r_cp_api_ybNOBb1X7NFK8

With RadioShack struggling, these things are getting harder and harder to come by. In my opinion, the best way to learn circuits is hands-on. The books are very well written, and get into circuit operation without dragging you down with the math that's behind it all. Totally worth $100.
https://www.amazon.com/Electronics-Learning-Lab/dp/B00A7AT41E

Them saying it "uses __ Watts of power a month" is nonsense, electrically speaking. A Watt is an instantaneous unit of power. A 100W light bulb is dissipating 100W of power at any given moment. Measure the voltage and the current and you'll calculate 100W, generally.

Power used over a span of time is called energy, usually measured in watt hours (Wh) or kilowatt hours (kWh), like what the electric utility bills you for. If you leave that 100W light bulb on all day, the energy used 2.4 kWh.

If the fence's maximum power consumption is 29 Watts, it doesn't make sense to say
"29 Watts of power per month". It would be 29 Watts a second, a minute, a day, a week, doesn't matter 29W would be used any time you measure it. Do you have a data sheet or something for the wireless fence?

For the sake of calculating your battery needs, let's say they just worded it poorly and the maximum power consumption is 29 Watts. And you want to run it for 2 days (48 hr). Battery capacities are usually given in Amp hours (Ah), which tells you the battery can supply this much current for this amount of time.

Some math:

Volts = 12V
Power = 29W (assumed confirmed?)
I(current) = P/V = 29/12 = 2.42A
Time = 48 hours

2.42 A x 48 h = 116 Ah

So based on the max 29W assumption, you'd need a 12V battery with a >116 Ah capacity, like this for example. Not cheap.

If it was integrated with a step down it would tell you can hook it up to a 120v.

Basically looking for a 24V, 125W or more LED power supply, can find them on amazon. something like this

There's cheaper options though.

Kill-A-Watt is what you're looking for.

The problem you're having with your power meter is power factor. If you multiply volts x amps, you get apparent power in VA(volt*amps). To get watts, you need to multiply volts x watts x pf. Pf is cos(Θ) where Θ is the angle difference between the voltage and the current. Here's a good explanation.

https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU

Plug it into this and give him the appropriate amount of money every month.