Hot, 25pe40vp chip (U2)

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PoltoS
Posts: 7565
Joined: 26 Jan 2011 19:36

Re: Hot, 25pe40vp chip (U2)

Post by PoltoS »

And please make a photo of Z-Uno from both sides to see if there are damanges or unwanted connections or shortcuts.
Geirbakke
Posts: 22
Joined: 22 May 2017 16:09

Re: Hot, 25pe40vp chip (U2)

Post by Geirbakke »

here are the schematics:

Image

the power are coming from my cabin 12v solar battery bank.
Last edited by Geirbakke on 05 Nov 2017 18:14, edited 1 time in total.
Geirbakke
Posts: 22
Joined: 22 May 2017 16:09

Re: Hot, 25pe40vp chip (U2)

Post by Geirbakke »

Cant se anything wrong with the z-Uno


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petergebruers
Posts: 255
Joined: 26 Jul 2015 17:29

Re: Hot, 25pe40vp chip (U2)

Post by petergebruers »

Can I make a general recommendation? Connect all pins of your Z-Uno to a 1K resistor. Doesn't matter if you use the pin as an input or an output. This resistor cannot protect you in all cases, but it really helps! The voltage drop across that 1k most probably is not going to cause issues, while it avoids latch-up or back-feeding the Z-Uno.

Was this built on breadboard? In that case, trouble with your ground connection might have pulled some ground wires above 3V. The reverse diodes on the pins of the Z-Uno would pass current to the power supply of the chip. With enough current (the Z-Uno needs less than 40 mA) the voltage could rise way above the operating range (2.8 V to 3.6 V). I do not know when it fries, it can momentarily sustain a bit more then 4 V, maybe 4.5 at room temperature, but that is out of spec and certainly not guaranteed.

With a 1k connected to a pin, and that resistor accidentally connected to say 12 V, you would get only about 1 mA injected...

But I see a more plausible explanation. Regarding pin 9 of the ULN2003. If a relay opens, the diode in the ULN2003 conducts and the current that was running through the coil now gets dumped onto pin 9, onto that red wire. According to your schematic, this wire goes to the 5V pin. correct? Nothing else connected to the 5V rail? I do not think there is a lot of capacitance on that 5 V pin, to take this current. So when the relays open, they could cause a high voltage spike on the input of the 3V regulator (derived from the 5V pin). This might have pulled the 3V regulator above the maximum rating, letting it pass a voltage spike...

Pin 9 in my opinion should be connected to the other side of the relay coil (the one that is common to all relays).
petergebruers
Posts: 255
Joined: 26 Jul 2015 17:29

Re: Hot, 25pe40vp chip (U2)

Post by petergebruers »

I think you might have killed the 3V regulator... if it failed "short" (very likely) between input and output, it now passes your USB voltage (4.5 - 5.0 V) at about 500 mA max to the Z-Uno, that is not good... I would not connect it to USB again unless you know the 3V regulator is OK!
Geirbakke
Posts: 22
Joined: 22 May 2017 16:09

Re: Hot, 25pe40vp chip (U2)

Post by Geirbakke »

Hi petergebruers,

If I understand you correctly, I should for safety reason connecting all pins, except 7-18,5v,GND and 3v3 to Ground with a 1K resistor?

I am not connecting the ULN2003 directly to the coils (this module have a seperate power supply):
Image

If, the voltage regulator are defective, wold the readings on the 3v3 pin be 4.5v?
petergebruers
Posts: 255
Joined: 26 Jul 2015 17:29

Re: Hot, 25pe40vp chip (U2)

Post by petergebruers »

Nu I meant 1k resistor, left pin goes to Z-Uno pin, right pin of the resistor goes to whatever you want to do with it. On your schematic, for instance, do not connect the switch directly to "D 9" but like this...

[ZUno D 9] ---- [ 1K ] ----[ Switch ] ---- GND

Although your ULN already contains resistors, I still would use such an extra resistor.

[ZUno D 22] ---- [ 1K ] ----[ PIN 1 ULN 2003 ]

If you accidentally connect the switch to 12 V, or accidentally touch your ULN 2003 with some (low) voltage source, it won't destroy your Z-Uno.

I put my Z-Uno on perfboard, and I connect all pins via resistors to XH 2.54 plugs so I cannot accidentally swap + and - or inject current into pins... Let me see if I can post a photo.

I recognize that module, I have something similar. To be 100% you should reverse engineer it, but I am almost certain it does not cause problems. All relays have diodes and the input is an opto-coupler. So that is why you need 5V... I see... How much current does it need, when all 4 relays are on? How much power dissipation does this cause on that 5 volt regulator? Or do you use an external regulator for this board? If that battery is charging, it could be more like 16-17 V, am I right?

If the 3V3 goes short, you would get around 4.5 V indeed. There are 2 Schottky diodes between your USB plug and the 3V pin (and the dead 3V regulator) so you see about 0.5 V drop...
Geirbakke
Posts: 22
Joined: 22 May 2017 16:09

Re: Hot, 25pe40vp chip (U2)

Post by Geirbakke »

Hi, I use a external voltage regulator for the relay module.
the changing voltage are never above 14.2V (AMG Battery) I have a solar regulator that regulate the changing.

I will change the setup to use 1K resistor on all pins like you suggested.
petergebruers
Posts: 255
Joined: 26 Jul 2015 17:29

Re: Hot, 25pe40vp chip (U2)

Post by petergebruers »

I hope it's only the 3V regulator that got damaged.
I am sorry, at the moment, I do not have an explanation for what has happened to your board...
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