Ok, I have everything ordered for my volt and amp meters. should have it all this week. During my time off I was thinking and I realize after reading a few articles that Im not sure about the difference between ground and common.. and how this works with +v and -v. I do know that I would prefer to have +-v rather than just gnd. and if it has +-v, where would I connect gnd. on the psu? I mean like if my psu has +-v, what is gnd. like if I was to hook up an led or motor to my psu where would I hook the + and - of them up? sorry for my lack of understanding in this area, I have been struggling to understand how this actually works.

 

Ok so heres where im at with my psu so far. any input? if I use a pass transistor on each lm317 I could get a max of 8a, but since im only shooting for 5 I figured this would be sufficient. This is only a rough draft. I still need to finish the meters, add a temp gauge using a lm35 and another 7107, add the adjustable current limiter, and add the protection circuits. I have an 8vac sec. coil which should be around 11.2vdc, I was thinking that I could use that to power all the 7 segment displays and maybe all 3 of the 7107's so I keep the H.V. sec. strictly for the psu output.. Any thoughts?

 

You can see the 7805 and 7905,Two 4 kinds ±5~15V fixed power, to see how the transformer and capacitors connections, also you can see the +V,0V(GND),-V.

And you just using the LM317 and LM337 to replacing the LM7805 and LM7905, the others are adding the 2N3055 to the LM317 and the 2N2955 to the LM317, or exchange them.

LM317 and LM337 dual power supply.

To make the real dual power supply as +,0V,- is better than just using two the same LM317 power to connecting to dual power as (+),(-),(+),(-) to +,0V,-V.

When you checked the real power circuit, then we can discuss your request.

 

Here is the another way that using NE555 to replace 7660 for negtive 5V.

 

I used the lm317's from the 317 datasheet specs, The only reason for the multiple 317's is to increase the current. I could vary the voltage with only 1 the same way but the current is limited to 1.5v. The datasheet also showed that adding a pass transistor can increase the output to 2a each. in your second schematic why the 317 on + and 337 on-? I noticed that your circuits provided less than 1a of current. That is my entire reason for using 4 lm317's. I was only curious about the relation to common and gnd. and the advantage of +,0,-.. I only want to have 1+,10,1- output. and have the voltage adjustable with a pot. Would the + and - adjust equally when the voltage is tuned?

 

Here is the another way that using NE555 to replace 7660 for negtive 5V.

that's very nice. I would much rather use a 555 as I have some experience with them.

 

I just want to start to build this, Im having a hard time getting everything together to even start. So exactly what is the advantage to a dual power supply or just the + - power supply? My main reason for asking about it is the 7107 has a -v input on it and im not sure how to get it.

 

If I split the out of the sec. on my transformer with the center tap, would it still put out the 60vdc after the rectifier?

 

I was posted on the #20, LM317 - output 1.2V to 37V, and some other else.
So if you want to reach to 50V then it will over the spec of the LM317.

Check the fifth circuit as following circuit.

7107 volt meter.

7107 amp meter.

ICL7107 based digital voltmeter circuit for several commonly used applications 3_1 - Setup for many current selection.

The circuit came from here.

The Amp Meter and Volt Meter connections.

Four kinds of transformers connetions.

 

The connections of Volt Meter and Amp Meter for one psu.

 

You need a center tapped transformer to make a +/- supply.
Check out page 2 of the data sheet. The maximum difference between Vin and Vout is 40 volts. You would be money ahead to buy a transformer that was right for your needs.

http://www.ti.com/lit/ds/symlink/lm317.pdf

 

You need a center tapped transformer to make a +/- supply.
Check out page 2 of the data sheet. The maximum difference between Vin and Vout is 40 volts. You would be money ahead to buy a transformer that was right for your needs.

http://www.ti.com/lit/ds/symlink/lm317.pdf

did you look at the schematic I posted a few posts ago? that is my actual transformer. it is center tapped on the H.V, sec. then there is 2 other sec. coils. the H.V. sec. is 44.5vac, the 2 other sec. coils are 8vac and 38.5vac. and from what info ive found on it, it should easily be able to handle the current demands. I was planning on limiting the voltage to 40vdc and current to 5vdc both adjustable. My design is in its infancy, the reason I posted it was so it could be looked over for flaws in the lm317t design and for suggestions to possibly make it a +/- supply. thanks

 

The connections of Volt Meter and Amp Meter for one psu.

thanks for finishing that for me scottwang. I haven't really got that far yet.lol.. Im still stuck at working the +/- supply in my circuit. im pretty solid on using the lm317's like I have drawn up, but I still need to make it work for dual supply.

 

Hello,

There are a couple of problems with your powersupply.
I made some remarks in your drawing:

Bertus

PS I made some typos in the drawing, but you will understand what is ment

 

bertus, thank you for the input, I cant remove the diodes, its actually a bridge rectifier pn:mb354-w. its rated for 40-100v 35a. How would I step down the voltage to get 40vdc before the 317's? I made the mistake of assuming that since I was going to limit the voltage to 40vdc on the output side that I didn't think about what was actually going to go to the voltage regulator.. I was also thinking that the voltage loss from the rectifier and filter cap would bring me closer to the required voltage.

 

I have a couple really nice 2200 ohm 5w resistors that are inside a cylindrical aluminum heatsink. would putting these before the 317's bring down the voltage and pass enough current?

 

Hello,

In case of a bridge rectifier disconnect the - connection from ground.

Bertus

 

at the sake of sounding like a complete noob, which I have probably already proven. If I take that connection away from ground, how is the rest of my circuit going to get ground? I was under the assumption that was where the ground for the entire circuit came from, the vac goes into the ac connections and the + and - for the dc comes from the other corners of the rectifier? sorry for all the questions, but this is the part that im having the hardest time wrapping my head around. Thanks

 

Hello,

In case of a bridge rectifier disconnect the - connection from ground.

Bertus

Thanks Bertus, that's my mistake.

 

ok, so after checking, my cool resistors are 25w but only 5 ohm. so I doubt they would work. So I need to get my voltage down after the rectifier and before the rest of the circuit.I wish I would have realized this before I bought everything. So what do I do now? I don't want to scrap everything and start over. and other than the input voltage, my circuit would work with the desired output. I only wanted 1.5-40 vdc at 5a. So now I need to figure out how to drop the voltage to 40vdc right after the rectifier. I don't want to change my transformer. It took me a long time to find this one.