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Topic: Arduino DUE overvoltage on analog pin, is there a fix? (Read 2626 times) previous topic - next topic

PDK91

So I accidentally put a higher voltage on my analog pin than suppose to. Now my processor over heats and computer doesn't detect it any more.  I was wondering if there's anything I can do such as replace a chip or etc. Also is there a list of chip components used on the board, like their part number.

 I'm probably out of luck and that's fine with me.

Thanks!

MrAl

Hi,


Wow, sorry to hear that news.  I hope you can get a new board.

If you replace the chip you'd have to find a way to install the bootloader too.  I dont know how to do that but maybe someone else here does.  If it is as easy as with say the Uno, then it will definitely be possible.

Doing the SMD rework with that 144 pin package isnt going to be easy though, you'd have to have experience in SMD work to do that.

The only method i know of to protect the pins from overvoltage is to use a diode clamp or make sure that the external impedance is high enough so that if an over voltage does occur on the input to the resistor network, the pin only gets a small amount of current even with an over voltage, and it gets clamped to the 3.3v supply.
For example, with a Schottky diode directly from the input pin to +3.3v and a 6.7k series resistor, a 10v input to the resistor will only cause 1m to flow though the diode and the input pin should only go up to about 3.8v or less (the absolute max spec is 4.0 volts).

I have been looking into this issue too for the past few days now.  I cant find any information about the ESD clamping diodes so i cant be sure yet if the ESD diodes will pick up that current and clamp the input to about 3.8v or less without an external Schottky diode.  This means i might just add the diode anyway and feel a little better about it.

I also plan to do a little test soon to find out if there really is a clamping diode internally or not.  Not sure when i will get to do this yet though.  In the mean time, adding an external Schottky from the pin to +3.3v and using a series resistance commensurate with your expected over voltage should help.

I may even go all the way and create a small 3.0v (or thereabouts) current shunt regulator and clamp all my used analog inputs to that, which would keep the over voltage on the pin itself to less than 3.5v.





MorganS

The Due doesn't have a bootloader. The chips contain that function from the factory and it's impossible to delete.

Even for experienced people who would consider desoldering that large chip, it's more economical to replace the whole board.
"The problem is in the code you didn't post."

MrAl

Hi,

Thanks for that bit of information.  So that means we could, if we had the means, replace the chip.

I did not check any pricing on the chip either though.  I would probably just get a new board too, but i do hate to waste a nice board like that.  I guess try to scavenge any other parts that are still good.
Is that a 12MHz crystal clock oscillator i see on the board?  It does not look like just a crystal.

Vaclav

Hi,

Thanks for that bit of information.  So that means we could, if we had the means, replace the chip.

I did not check any pricing on the chip either though.  I would probably just get a new board too, but i do hate to waste a nice board like that. I guess try to scavenge any other parts that are still good.
Is that a 12MHz crystal clock oscillator i see on the board?  It does not look like just a crystal.

but i do hate to waste a nice board like that.

You already did.


Go for it, replace the chip , if you want to do the chip replacement as a personal challenge.


EEPblog

i reccomend next time putting a 3.3 (or max. 3.6V) zener diode facing from ground to the adc. This way if you put voltage higher than 3.6V it will clamp it down. You can use it also for i/o pins, however it won't trigger the pin if your diodes kick in and start protecting against overvoltage. I have in plan to do a shield for due, that'll make the due 5v compatible.
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davidreeves20

Have you tried clamping the voltage to 3.3 or 3.6?  What zener do you use?  Does it impact your analog reads?

I have also had a similar issue to the OP (but with ADS1115 ADC) and been interested in protection but haven't got a working solution YET.  I did try a IN5226B which I thought was 3.3V Vz zener but realized it starts opening at lower voltage so ruins the voltage.  Maybe a different zener would work.

A schottky diode to the 3.3v rail won't work because of leakage current.  I want to ensure nothing over 3.6V.  Another thought is to use a signal diode like a IN4148 to a clamping rail at 2.3V or so should limit to 3.3.  Or maybe a NPN transistor like a 2N3904 with the base and collector to the analog pin and emitter to the clamping rail.

LMI1

but i do hate to waste a nice board like that.

You already did.


Go for it, replace the chip , if you want to do the chip replacement as a personal challenge.


The pins of Due are quite densely on chip. You can't solder them invidually.

If you can get the old chip off and the still have the PCB ok, you can use a hot air solder station and flux to solder new chip.

Some have also soldered these kind of chips with ordinary soldering iron. I have not tried it because it looks impossible, but my friends have done it. You just have to fix all the shorts later. And some soldering irons and their tips are better than others and so on.

So it is not impossible to hand solder those kinds of chips but it is a skill you have to learn first. But is it cheaper than a new Arduino DUE board.


MrAl

Hi,

I think the prices for a new chip start at around 10 dollars USD.  You also have to figure in the fact that the replacement might not be successful and thus a complete waste of money.

It's a shame that there is not more protection for those special pins.  I also tried to find out more information on this but none of the companies involved are very cooperative.  It's almost like they are ashamed of what they made.

If you use a zener or better yet several Si diodes in series as a zener, you also need some impedance in between like 1k resistor or better 5k or 10k if you can get away with it.  That's because if you over power the zener or diodes the voltage will still go too high.

On the Microchip PIC chips (mid range chips) they specify the max input current for the input ESD protection diodes so you can easily determine what the input pin can take and what it cant take.  You can then settle on a series resistor value vs your expected max input so you never blow the pin.
Their rating is 20ma max, so you know what values to use from that spec.
With the ARM chip, it's almost impossible to calculate accurately, so you have to supply your own clamp like with the diodes.
BTW, regular fast Si diodes have a sharper curve than most low voltage zener diodes so they clamp better.
You just have to have enough in series to make up the voltage you need.
They should be the fast type though like 1N4148 not ordinary rectifier diodes.
Of course temperature is a consideration too, so for wide temp swings you might have to go with an active clamp like a TL431 shunt regulator with series resistor, or something made commercially for this purpose.


BenKissBox

#9
Jan 08, 2016, 01:22 pm Last Edit: Jan 08, 2016, 01:28 pm by BenKissBox
Apparently, you killed the diode on the input (within the chip, so it makes a short-circuit between Vcc and Gnd, that's why it heats now)

Technically, you can replace the SAM3X, but not sure it will be valuable in terms of economic balance. A new SAM3X costs already 11 euros from Mouser, without the packaging costs. And you will need to buy some extra stuff for the soldering (expecting you have a thin soldering iron)

You can replace a LQFP package without an hot air iron, but you need a very thin tip on your soldering iron. Personnally, I use 0.8mm Antex tip for that. The second thing that you will need is unsoldering braid and soldering flux (if possible, the "no clean" type). You will also need a small cutting plier (with the smallest possible extremity, to work near the component body). This will be probably the most expensive tool you need to buy

The flux is sold in various formats, the most useful is the pen model. DO NOT TRY TO WORK WITHOUT FLUX! With such compact packages, you have no chance to avoid solder bridges between pins, and that's where the flux comes into the game.

First you will need to cut all the pins around the SAM3X, in order to remove the body. For that, use the micro cutting plier to cut the pin at body level. Take care not to bend the pins too much, otherwise they will pull on the copper track and there is a risk to damage it.

Once the body is removed, use the iron to remove all the pins, one by one. This is rather quick to do, just use the soldering iron for that.

Next step is absolutely mandatory : you must clean the pads where the chip was soldered. To do that, use the flux, spread it over the 144 pads. The flux will help the solder to melt and clean the pads. Use the soldering iron to melt the solder on the PCB and use the unsoldering braid to remove the old solder. Take care not to overheat the PCB. The best thing is to clean 5 or 6 pads, then let the PCB cool down for a few seconds before you do the next ones

Once this is done correctly. you shall have a perfectly flat PCB where the SAM3X was soldered. If not, then you will have the biggest problem to solder the new chip, because all the 144 pins must be aligned on the same plane.

Clean the PCB to remove the flux with solvent (the flux turns brown and becomes sticky once the soldering iron has used it)

Put some clean flux on all the pads to keep them clean for the next step.

Put the new SAM3X on the PCB, and make a tiny solder point on two opposite pins. This will hold the chip while you solder all the other pins.

Apply flux on the pins of the SAM3X. Do not hesitate to "moisten" the PCB. It's better to have more than not enough.

The next step is also critical and shall be done as fast as possible. You will need to solder all pins by moving the iron. It shall be slow enough to let the solder go on the pin but fast enough not to heat the chip too much. A good method is to make one side, let chip cool down, second side, cool down, etc.

During this phase, make sure that you put enough tin on the pins. VERY IMPORTANT : it does not matter if you make bridges between pins. It's better than having not enough tin and make a bad soldering joint.

And last step : using the unsoldering braid, remove the solder in excess. With the flux, the solder will go between the pin and the PCB pad, and that's where it is important. The braid will remove what is in excess, not what is under the chip.

And you are done....

As you see, it's possible to replace the chip, but you will need tooling that is not so common with amateurs and rather expensive. And you need to get the "touch" to do that. It's not hard (I am soldering 0.3mm pitch chips on prototypes following this method) but there is a serious risk to fail the first time.

So.... good luck

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