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Help! (5V psu problems) Answered

Help!

I'm trying to make a 5V psu for programming my new (but not so shiny v_v) ATtiny2313's

I've got the circuit shown below set up, but I'm getting out around 5.6V, when the spec sheets say that I'm supposed to be getting out 5V (+/- .2V) I'm using the LM 340t5, just 'cause I don't have any other regs (except for the MC78M05CT, which is basically the same thing.

Any Ideas?!

EDIT


I know what was wrong - it was my meter, it really was 5V all along ;)

19 Replies

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zachninme (author)2007-10-07

I told him, just use 2 AA's!, or 3! The ATiny's will be fine as long as you keep it under 5v.

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T3h_Muffinator (author)zachninme2007-10-07

Guess what?! I got it to work!

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Goodhart (author)T3h_Muffinator2008-01-03

What did you do differently ?

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T3h_Muffinator (author)Goodhart2008-01-03

I replaced the batteries on my meter ;-)

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Brennn10 (author)T3h_Muffinator2008-01-03

I have never implemented a transformer into any circuits I have done, but to get my definition straight, is the transformer taking the 3V (from the 2AAs) and raising the voltage to ~5V? If my definition of a transformer is correct, it raises and lowers electricity. Correct me if I am wrong. I am somewhat confused.

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zachninme (author)Brennn102008-01-03

Transformer keeps Wattage (Voltage * Current) the same (in reality, the wattage goes down a little) it just shifts voltage to current or vice-versa.

However, its only for AC ;-)

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westfw (author)2008-01-03

Looks like it should work to me. Are you sure your meter is accurate? Got the right pins in the right place? Does the 78M05 behave the same?

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T3h_Muffinator (author)westfw2008-01-03

It was my meter - the batteries were low and needed to be replaced.

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CameronSS (author)2008-01-03

I'm not too good at reading datasheets...What is the difference between an LM317T and an LM340T? Is it just a different amperage rating, or what? Could an LM340T be used interchangeably in a circuit designed for a LM317T?

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Goodhart (author)2007-10-06

Are you testing "under load" ?

Is this the data sheet you refer to ? LM340T5 Data Sheet Link

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T3h_Muffinator (author)Goodhart2007-10-06
Yep, I'm testing it under load and that's the data sheet I actually got it to regulate 7V when input is 9Select as Best AnswerUndo Best Answer

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Goodhart (author)T3h_Muffinator2007-10-07

Something doesn't sound right. Either the regulator, or how it is configured in the circuit.

Output Voltage 5V 12V 15V
Input Voltage (unless otherwise noted) 10V 19V 23V

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T3h_Muffinator (author)Goodhart2007-10-07

yeah..... it's pretty weird... I'm just using 2AA's for now, but I'd like to get this reg working eventually... The circuit is definitely correct.... might just be the reg. I'll see if I can get my hands on a 7805

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whatsisface (author)2007-10-07

I don't understand why you're using this schematic.. Do any other circuits work properly?

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user

that's pretty much the same thing as mine, but my dad (EE) says that the 10 uf will steady the low freq waves. oh, and the diode's an LED, just a power light. Nothing works with this as of now. Except..... I tried using the MC78**5 and I got it to regulate at 7V, even though it's supposed to be regulating at 5....

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schorhr (author)2007-10-06
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its a lion (author)schorhr2007-10-06

may not have helped t3h_muffinator, but that was exactly what i have been looking for (well not really looking but thinking about looking for). thanks.

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T3h_Muffinator (author)schorhr2007-10-06

Yeah, I know...... but I don't have the 7805..... I'm stuck with these ancient ones

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