LM317 2N3055 Variable Circuit Problems

[duke37]

And again the 317 and 10k pot fried just like overloading ??????

Then you are using too high a voltage or your connections are wrong.

If the 317T is placed on its back with the writing visible and the heat sink to the top of the page, then the connections are:-
Left adjust
Centre Vout
Right Vin

Get the supply working without the 2N3055 transistors first then add them.

 

[davenn]

Then you are using too high a voltage or your connections are wrong.

If the 317T is placed on its back with the writing visible and the heat sink to the top of the page, then the connections are:-
Left adjust
Centre Vout
Right Vin

Get the supply working without the 2N3055 transistors first then add them.

This, I have been saying all along

There is absolutely no way the trimpot can fry if it and the 317 are connected correctly

 

[heavyfletch2nd]

I know I am doing somthing wrong I just dont know what it is "fustraiting" lol but its how you learn or how im learning . 22v on main rail should be fine for the lm317t ,I have checked vin and vout lots of times , im using the correct resistor red violate brown gold between adjust and vout , I am using a 10uf 25v cap from ground to vout ,I am using a 10k pot going from ground going to the adjust pin , all ground points are on the
Ground rail , I know im doing somthing wrong or it would work . I have wached loads of videos and researched a lot now so I understand how things work and what their functions are and what their pin lay outs are . "I didnt when i first started i have almost memorised the resistor colour bands now "it soon sinks in when you make loads of mistakes lol" I can do it in the bread board but not in the prototype board . It is always in the adjust pin of 317 where it smokes then pot smokes too . Thank you all for replying to this thread I have learned loads in just two weeks . I have had to order more pots and 317's .

 

[Bluejets]

Another piece of advice.....not a good idea to connect a microcontroller charger to a supply that is above the rated input let alone one that is diy with problems.
Otherwise you stand a good chance of smoking that as well.

 

[ModemHead]

Get the supply working without the 2N3055 transistors first then add them.

This is absolutely necessary. With 22V in, the LM317 output should adjust from about 1.3V to 20.5V as the pot goes from min to max. It should reach max voltage at around 42% of full rotation. If you set it to 12V, you should be able to connect and run a small load like a computer fan from the LM317 output. The voltage should drop very little when the load is attached, and nothing should overheat or smoke. If it won't do this, there's no need to connect the 2N3055 transistors.

This, I have been saying all along
There is absolutely no way the trimpot can fry if it and the 317 are connected correctly

This is definitely true as long as the LM317 is functional. However, if it welds itself into a short-circuit, all bets are off and the smoke comes out when the pot is turned down near zero ohms.

Another piece of advice.....not a good idea to connect a microcontroller charger to a supply that is above the rated input let alone one that is diy with problems.

Yeah, don't blow up the Turnigy. Find some automobile lamps for testing. A standard 60W headlight is a 5 amp load. An 1156 or 1157 tail lamp is about 2 amps or so. Connect bulbs in parallel for more loading.

 

[heavyfletch2nd]

Yes perhaps I am trying to run before I can walk properly , I'll slow down a bit and try some car bulbs , I have had a 2n3055 wited to the bread board emitting and adjusting properly I cant seem to find what im doing wrong when moving to the prototype board ,I thought about adding additional lm317 to cope with the transistors but then I thought I'll be going through them 2 at a time lol , in the prototype board there are four caps and a different transformer thats all but circuit is the same , well third time lucky I hope , I can see me finding somthing really simple and stupid I have probably done then I'll give myself a black eye for being a dick lol. but I am enjoying learning and you guys have been a mint source of knowledge im glad I came on this site and had all of you to ask . Massive thanks I really have learned a lot more than I expected . We will get there in the end.

 

[Bluejets]

Perhaps a second set of eyes on the job, one set reading out the point to point wiring, the other checking.
Works sometimes.

 

[heavyfletch2nd]

A little off subject but I thought I'd share to my helpers , my daughter turned me into a grandad today lol

 

[hevans1944]

Congratulations, Grand Pa!

 

[(*steve*)]

Congrats

Do you have the datasheet for that device?

You have to satisfy the input requirements, the output is frequently activated and there is very little control.

 

[BobK]

Also, audio output is easy to achieve but hard to suppress in that type of device.

Bob

 

[heavyfletch2nd]

Thanks fellow granpas lol Back again with the new bits for another round of electrical fun/smoke , no steeve I don't get a data sheet when I buy theese parts, I have seen them on the internet tho but I dont really understand the bar charts I just look to see the pin layouts , I am going to add a pic of what is in the bread board now , the wall adapter I am getting the power from is 10v 1.5a , the resistor in the pic is a 270 ohm like it says to use on the original diagram you all probably know by looking tho , the pot is a 10k pot also like it says in original diagram here is the pic↓↓↓
this still fried the pot!!

 

[BobK]

That appears to be wired correctly. The only way it is burning the pot is if either the resistor or the LM317 is shorted.

Try it with a 1K resistor instead of the pot. You should get about 5.8V out if everything is working correctly. And if you burn the 1K resistor, it must be that the power supply is greater than 10V.

Bob

 

[heavyfletch2nd]

I tried a new resistor a 1k 1% the pot still smoked , it does adjust but extreemly sensitive only quarter of a turn it smokes when turned to minimum volts , I should have 5 more 317's tomorrow im going through these things like a kid eats sweets lol good job they're cheap . How can I check the lm317's are ok , i have 2 that didnt seem to fry but they may have inside this one in the pic is one of two that didnt burn ,the 10v supply I am using is showing 13v off load but the lm317 should cope with 37v fine . We will see tomorrow when the new ons arrive I suppose

 

[duke37]

I so no output capacitor.

Can you find someone local to you to help?

 

[Bluejets]

There are many things not shown in your photos and as such, many things are assumed by those here as being correct.
It may seem unimportant to you BUT you do have the problem and as I see it, these assumptions are the root of the problem.
As an example the mix up over the resistor required from output to adjust.
In your latest photo, no item values/types can be seen along with some of the connections, the details on the power supply, what you have connected to the output and what settings you are running on the meter.
OK it does show some connections but not all.
You quote the values of certain items but are they really those values or have you made other errors there.
Do you see where this is going?

Edit: As a side note, 270r resistor is the only load I can see and this will be well below the minimum current required.(1.25v ref/ 270r = 4mA) Specs say 10 to 1500mA.

 

[ModemHead]

Wiring looks ok from what I can see.

Turn the pot up high enough that it doesn't smoke. Power up and measure voltage from LM317 pin 2 to pin 1. It should be exactly 1.25V. If not, the 317 is probably toast. In a properly working LM317 circuit, this voltage should always be 1.25V.

4.6 mA is above the typical 3.5mA min load, it should be good enough for now.

 

[heavyfletch2nd]

Juke ,I do use a 10uf 25v cap in the prototype board I'm just getting things the right way in the bread board first to try and prevent frying transistors again, I have made too many mistakes not knowing enuf so I'm going to slowley build step by step with all you guys so I know exacly what does what and why it is doing what it is and hopfully learn a lot more, I dont know any one into electronics near me (worcester) , I wish could go to back to college lol but im 40yo bit old for that now , every one on here has a lot of good points for me to prossess try out and learn from , its the mathematics in all this that seems to be very important I could probably do the math if I could work out where you guys pull the numbers from and how and when do you decide you are multiplying deviding subtracting etc I have been looking at ohms law but cant get a grip on it lol I am trying to understand it all im waiting to see some kind of system or somthing to click in my head if you know what I mean . Blujets, yes I think i can see what you mean and I'll add another photo or two tomorrow of the old wall adapter im using and meter setting I have it on in the bread board for you to see , I have that big transformer for the actual build I wouldn't be able to tell you anything about that appart from 16v off load 15a thats what I was told from who I bought it from , just a thought on what i think your saying wich does seem to make sense to me "if I'm starting to understand" do you think it would be a good idea "in the actual build" to run the cooling fans off the lm317 pin 2 to get the load then it would have a constant load 0.125ma per fan I have two fans and what ever the 4 transistors pull to operate . Modem head ,thanks I'll test the volts there .

 

[duke37]

You obviously need some instruction, 40 years old is nothing. I am twice this and still learning.
Belper is a bit too far from Worcester for me to help directly.
Ben Nock in Kiddy may be able to help you find someone.
You could look for the local radio club at the RSGB site. Some do courses for the amateur radio licence, they start at the very beginning (a very good place to start) for the novice licence and deal with circuitry and soldering.
It is very satisfactory when the penny drops.

I do not think you have 0.125mA per fan, that is very low. Perhaps 0.125A or 125mA?

The idea of using a fixed resistor (1k) instead of the potentiometer is a good one, you could then change to the pot when things are working properly. There will be 125mV between Vout and Adjust so with 270Ω there will be a current of I = V/R = 0.125/270 = 0.5mA, this is too low for a load so put a led with a 1k resistance in series as a load where you can see the action.

 

[ModemHead]

Vref for an LM317 is 1.25V, not 0.125V.