Ethermega fried the 5v regulator

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dstorey
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Ethermega fried the 5v regulator

Post by dstorey » Fri Sep 21, 2012 11:57 pm

Hi all

Looks like I fried my Ethermega's 5v regulator - the EUP3476. I get no life when powered from the DC socket but it works fine from the USB (yes, I switched the jumpers). I can't seem to find a sales outlet for this component. Anyone know where I can buy one from or does anyone know an alternative part?

thanks Dominic

dstorey
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Re: Ethermega fried the 5v regulator

Post by dstorey » Mon Sep 24, 2012 11:43 am

A question to Freetronics Employees:

Can anyone help me here? Not heard back at all from you - you guys are very happy to sell me new products (I get sales emails back promptly!) but when it's something a bit more difficult, I get no answers. I have mailed you more than once on this subject.

I'm happy to pay shipping and buy the EUP3476 regulators - they are just simply not available from any outlet I have tried.

Can you help please?

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jonoxer
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Re: Ethermega fried the 5v regulator

Post by jonoxer » Mon Sep 24, 2012 12:10 pm

Hi Dominic, I've just followed up via email. We'll post you a couple of replacement regulators free of charge.
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effgee
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Re: Ethermega fried the 5v regulator

Post by effgee » Thu Sep 27, 2012 7:41 am

Hey Domenic

do you know what fried your reg ?
The datasheet http://www.eutechmicro.com/PDF/EUP3476.pdf suggests its rated at 3A output.

For a minute there I was considering using the 5V output of that reg to supply power for a stepper (via a Pololu A4988 breakout board, currently running on 24V, long story)....until I found myself typing it, and thinking what horrible effect it may have on the microcontroller.

p.s. Jon - there's a minor typo on the EtherMega schematic for that chip, says EUP3476SO08T, presumably should be ...SOP8T. I only comment 'coz it made it a little harder to find the datasheet.

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jonoxer
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Re: Ethermega fried the 5v regulator

Post by jonoxer » Thu Sep 27, 2012 8:13 am

effgee wrote:there's a minor typo on the EtherMega schematic for that chip, says EUP3476SO08T
Thanks for pointing that out, I'll check it out on the schematic. Perhaps I was floating along on caffeine and sugar and lack of sleep when I did that footprint!
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effgee
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Re: Ethermega fried the 5v regulator

Post by effgee » Fri Sep 28, 2012 12:46 am

jonoxer wrote:caffeine and sugar and lack of sleep
I hear you there - seems to be the only way to get things finished, sadly.

Any comment on my harebrained thought of pulling maybe 1 to 1.5A from that reg for my stepper drive ? I've got a couple of 47uF caps on the feed to the stepper drive, that should help.

I guess the best thing is to give it a try with a scope on the 5V line, but the project is elsewhere right now, and I'd hate to fry something out of curiosity.

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Re: Ethermega fried the 5v regulator

Post by jonoxer » Mon Oct 08, 2012 3:15 am

The EUP chip is rated to that, but it's also dependent on the current rating of the inductor and the thermal dissipation of the board. Because it's quite tight I had trouble getting long copper runs out from the thermal ground of the chip, so it's certainly not as good as if the chip was on a big blank bit of PCB with plenty of copper connected. It shouldn't be too bad though.

The inductor is rated to 3.5A.

I'd put the scope on it and give it a go, as you suggest. Some good decoupling caps would be an excellent idea though!
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Jon

effgee
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Re: Ethermega fried the 5v regulator

Post by effgee » Tue Oct 09, 2012 12:51 am

jonoxer wrote: give it a go
Jon
perfect timing; I'll get a chance to try it this afternoon with luck.

thanks again for the great support

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Re: Ethermega fried the 5v regulator

Post by mjoconr » Fri Mar 29, 2013 5:59 am

dstorey wrote: Looks like I fried my Ethermega's 5v regulator - the EUP3476. I get no life when powered from the DC socket but it works fine from the USB (yes, I switched the jumpers).
It seems like I have just had the same problem. I was working correctly and I came back and found the unit unpowered. Plugging in the USB and it works again. (after moving the jumpers)

I'm supplying 8 volts. No real curren is being drawn from it as we only have a few BUZ71 Fets and a 1.5 volt solar panel for an analog input.

Is this a common problem ?

Mike

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Re: Ethermega fried the 5v regulator

Post by cef » Fri Mar 29, 2013 7:11 am

Hi Mike,

From what I believe this is not a common problem, but I may not be across everything, so hopefully Jon will reply to that question.

If anyone gets this issue and wants to confirm if the regulator is working, you can put a multimeter between the DC IN pin (on the jumper header that selects between USB / DC IN power) and Ground to see if there is any voltage coming out of the regulator.

Other things of note:
The DC jack on the board is protected from reverse polarity by a 1N4004 diode, but the VIN pin is NOT. If you put a negative voltage on the VIN pin (between Ground and Analog 0 on the shield header), you may fry the regulator.
The 1N4004 diode will drop somewhere between 0.8 and 1.1 Volts. The regulator (EUP3476) seems to need at least a 0.8 Volt difference between input and output (at least, the way I'm reading the spec sheet) so you probably need a supply a minimum of 1.9 Volts higher than what is needed out (5 Volts in this case, so 6.9 Volts in) if you use the DC Jack. Note that while a DC plugpack may say it supplies a specific voltage, that may be only under ideal conditions (eg: exactly 240V supply, no load, etc), so you may want to check your actual input voltage under load (eg: across the DC Jack pins while plugged into the EtherMega) if you have issues.

PS: Some DC plugpacks with no regulation will give you the rated voltage when the input is 240 Volts, but if the input drops (220-230V is not uncommon in Aus, and in older places with bad wiring it can get even lower), then you may have issues. What you get out of the power point can be also dynamic due to the nature of the power lines (someone else using lots of current puts a load on the line, dropping the voltage for everyone on that segment). This can be be a real issue in the outback where 250-260V is common on a lightly loaded line until something on that segment draws a large amount of current, dropping the voltage quite dramatically. If at all possible, I recommend you use a regulated plugpack, as this should avoid most of these issues.

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