Dragon Vtg shorted to ground

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The other day I was using an AVR dragon, and for some reason the voltage regulator in my project (24V to 5V) outputted 24V at the 5V output going to Vtarget. Consequently, I cannot use the ISP function of the dragon anymore. When I tested with a multimeter, it seems Vtg is now shorted to ground (and this is without anything connected). Upon plugging in a micro (it obviously draws more current then it needs) and the voltage sensed is like 2.5V instead of around 5. Is there any way to repair this? JTAG still works fine, but not ISP. I have read a lot of the popular sites on the internet about dragon repair but have not understood any of it to be particular to this problem. Why do you think Vtg now shorted to ground because of the 24 volts?

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You fried it.

See my signature for possible fix

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tessa and Tina, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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Lol ok, figured. Btw plons I talked to you about a fried dragon that I had before, that was a different one (this is one at my work lol).

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Oh and I was wondering, how beefy is the JTAGICE mkII as far as protection from things like this?

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Oh, it's beefy, but 24 Volt will kill it too !

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tessa and Tina, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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You shouldn't use such a big differential between input/output of a voltage reg., in the future. That's where the problem started, it probably gave out after too many times of excessive power dissipation. What was the 'lifespan' of the voltage regulator circuit ?

1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1

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I don't know what the lifespan of the regulator was but I was using an LM7805

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Quote:
I was using an LM7805
WITH a heat sink?

--greg
Still learning, don't shout at me, educate me.
Starting the fire is easy; the hardest part is learning how to keep the flame!

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No, no external heat sink.

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Will you use one next time? ;)

--greg
Still learning, don't shout at me, educate me.
Starting the fire is easy; the hardest part is learning how to keep the flame!

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gregsmithcts wrote:
Will you use one next time? ;)

Lol yes.

indianajones11 wrote:
You shouldn't use such a big differential between input/output of a voltage reg., in the future. That's where the problem started, it probably gave out after too many times of excessive power dissipation. What was the 'lifespan' of the voltage regulator circuit ?

The 24V input is a must, what would be the suggested alternative circuit?

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Quote:
would be the suggested alternative circuit?
An adequate heat sink is all you need.
There are several ways to drop the voltage prior to feeding it to the regulator, but all of them will create heat.

--greg
Still learning, don't shout at me, educate me.
Starting the fire is easy; the hardest part is learning how to keep the flame!