Don’t worry about mixing things in threads. This community is quite relaxed in these matters in my experience.
Maybe during the experiments you can reduce the inrush current by leaving out some of the capacitors. Then the inrush current will be lower and you can more easily test the rest of the circuitry using one of the suggested methods.
Mine puts out 8.3 amps or 100 watts of power.
I’m not sure whether this is a bit about semantics, but maybe also to clarify things a bit. What you mean is that it can output a maximum current of 8.3 amps. It does not output 8.3 Amps of current if there is no load. This will only happen if there is a load that draws that much current. If you connect an LED and a series resistor to it, all that will draw is a few milli amps.
The other thread mentions toroid transformers, which have higher inrush current than ordinary transformers (with the multiplier increasing by size; large ones can need hundreds of amps for a few milliseconds, but then you’re in “please talk to a qualified electrician” territory).
I don’t think a few millifarads extra on the low side should be that much of a problem if the fuses are properly dimensioned, but the extra inrush current on the mains side might be a problem (but 100 VA should be manageable, though, unless perhaps if you have undersized and/or fast fuses on the way in).
@fredrik So one way of approaching this is to leave the transformer connected to the mains and add a switch to the secondary side as an alternative on/off switch.
The transformer itself looks like a normal tube fuse at 10amps. However; I am not sure this is the which side of the transformer its on. I could test this with resistance by removing the fuse and looking for a missing value. I am using basically fast burn auto fuses at 2amp. I also can use two switches if you guys think this will help make things easier. I have been in electrical school and past the first semester. Unfortunately I was too slow at learning the NEC math. I got yelled at by my teacher for becoming confused and for putting the class behind. Long story short I dropped out because my emotional health was scaring me. A story for another time.
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I am aware of how this works on a basic level. I am not perfect with transformers and analogue just yet. You guys lead the way. I will fallow where I can. I can’t complain when people are willing to teach me. It really means a lot to me.
My cell does not like my PC and have to edit
here is the breadboard I have it on. I am using blade fuses on pinch clips. The 10amp fuse is inside the transformer.
If the transformer is the ‘size’ you are describing it, you need not worry about the transformer. It can stand a bit of trouble. It is more that because of its high power it will not stop and fry everything that is connected to it if the secondary current gets very high. It will probably humm a bit and get warm. So I take it the fuses were the one between the transformer and the circuit. Did I understand this correctly?
Ok, I see the fuses now. They are on the secondary side of the transformer. But I do not see a bridge rectifier or a set of 4 diodes. Whereabouts are they in the picture?
Yes, you are correct. Kind of like plugging a rotary tool in with a radio. The radio burns out because of the high draw from the rotary tool. Same thing right? Also the extra caps were not connected during the trouble shooting. I was trying to start another idea and sort of wanted to do more reading before I tried anything. The new idea was to create a capacitor bank at something like 5amp blade fuse and then connect that to the 2amp fuse. Not sure if my idea would have solved anything if its a large current draw.
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Edit
The rectifier diodes are on the voltage regulators and two for before the input on the capacitors. Let me get a pic real quick
Given that the power supply contains 2 distinct parts, one for a positive and one for a negative output voltage, I think it is wise to concentrate on one and once that is working concentrate on the other.
Because it is difficult to follow the wiring via the pictures, I would advise to start with the positive supply part and get that to work and then as soon as it does, start on the negative supply (without changing anything in the wiring of the positive supply). In my experience if you approach a problem systematically, don’t skip any steps or make no assumptions, this will often lead to a solution.
And while you are experimenting, keep in mind to only change one thing at a time and see what that results into. If you change more things per try, you will not know what it is that caused the result ( whether it was a success or not, and you miss the opportunity to learn from the try ).
@LP2Lily I’ve changed the description of how to use the resistor to measure the current a bit in the 5 alternate ways message above. Of course if you have a meter that allows you to measure current directly, that is also what you can do.
Unless you have a clamp meter, measuring current by measuring the voltage drop across a known resistance is usually safer, both for yourself and the multimeter – forgetting to move the test leads from the 10 A input back to the V/mA input is a great way to short things the next time you try to measure a voltage, and forgetting to move the test leads from the V/mA input to the 10 A input when measuring current is a great way to blow the fuses in your multimeter (and they’re often expensive, at least if they’re good enough to actually protect the multimeter).
A friend of mine once switched the current meter we were using to measure the current running through the rotor of some type of AC engine ( a huge machine weighing hundreds of kilos fastened to a block of concrete ) which was showing 4.5 Amps at the time in the 5 A range of the meter to the 1 Amp range. This made the fuse of the meter blow. And as a side effect the engine ( I forgot what type it was ) started to speed up. This is typical for this type of engine, break the current through the rotor and it speeds up and doesn’t stop. And it would have tried to speed up ad infinitum and possibly would have broken loose from the clamps holding it to the floor had not our teacher hit the power button of our experimental setup. I still remember his words: “You better check your circuit, gentlemen” he said, turned and walked away. He had obviously been waiting for this to happen to someone in this class.
I got to looking at the links that I was given. I also searched around on eBay. I managed to find class A transformers. If I wire the up in the configuration noted in the picture would this work? Also are the amps added for the total? I decided on using my other transformer to put together a bunch of desk lamp lights. Should make a good conversational piece. LOL
eBay Listing
Description Primary Input Voltage 117VAC, Output Voltage 24VCT (-12_0_+12), 2A, 24VA, Solder Lug/Push-on Terminals, Class A Rated @ 105ºC Insulated , 1,000 Volt Hi-Pot Tested. 2.79" mounting hole center-center, physical size 1.95" x 2.32" (no tabs), Height 2.00".
The 3 next to the hashed line means 3 conductors zip tied. This is a common notation for digital circuits in case anyone is wondering.
Looks good to me. You might consider giving each transformer its own fuse. Now if the one fuse blows, none of the transformers gets any current. In case every one has its own fuse, problems with one part of the setup will not influence the other parts.
I’m planning to put an FC Power board in my next case, with a 2.1 mm barrel jack in the side of the case. What gauge wire do I need from the jack to the board? I have a 2A wall wart which I hope to use with at least a couple FC boards later on.
I like to oversize so 14-16, maybe 18 AWG? (lower is thicker). Easy to source (these dimensions are common for extension cords, basic mains wiring, automotive cabling, etc) and plenty of margin.
This page has a table with current limits and a voltage drop calculator.
(as you can see from the table on that page, you can go quite a bit thinner before you’re outside the (usually very conservative) ampacity guidellines, but why take the voltage drop if you don’t need to?)
Oh, now I need to worry about that too! xD I just checked and I am using AWG 23, which is only 0.73A :-/ Need to replace those, I think… What does the “Maximum amps for chassis wiring” mean? I found something that it means that each cable is wired separately and not in a big bunch, but it seems to be a bit vaguely defined. Then it would be ~4A and I am happy with that…
Quick check: do the wires warm up enough that they feel noticeably (*) warmer than the rest? If so, you’re may want to change them at some point. But you’re probably fine.
You could also measure the resistance, but measuring very low resistances is a bit tricky unless you have a meter that can do kelvin sensing (using four cables instead of two).
(*) intentionally vague here, since your skin is very very good at detecting tiny temperature differences, and there’s always some tiny energy loss when current goes through a piece of wire. It’s larger losses that’s a problem.
The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle.
Now we get to argue over whether two wires is a bundle.
18 AWG is 2.3 amps by the “very very conservative” rule so I think I’ll probably use that. About 0.05V drop for 2 A over 2’ one way.
On a related note, I looked at the connector listed in the FC Power BOM, and realized it, like most of the other barrel connectors at Tayda, has NO specs for maximum voltage or current. The “datasheet” is nothing more than a dimensional drawing. The other ones that do have specs seem to be either maximum 12V or maximum << 2A. Mouser has less sketchy options.
Hi everyone! I am searching over Internet something but couldn’t find any answer! So I thought here was the good place!
So I plan to buy a power supply to try DIY modular so I need +12V/GND/-12V
Sooo I wanted to buy those power supply and thought that the gnd terminal was 0v and negative and positive terminals were -/+V but apparently not?
Thank you if someone understand my problem
(and they’re often expensive, at least if they’re good enough to actually protect the multimeter).
