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#1 2018-07-29 10:57:24

piwi
Moderator
Registered: 2013-06-04
Posts: 524

Poll: Is your Proxmark3 overheating?

Trying to nail down and fix the overheating issue mentioned in http://www.proxmark.org/forum/viewtopic.php?id=5506:

* Continuously usage will cause overheating, so try not to use it under crazy conditions (Under the sun or extreme condition)
* Official Repo will cause overheating, since it is quite lax in turning off the antenna.

Just try not to push the proxmark3 too hard under extreme condition. It happens on all revisions of the proxmark3 device.

To all those who experienced such issues regardless of the Proxmark3 version:

  • Under which conditions did you experience overheating (which commands did you run) and how long did it take until it overheats?

  • How does it materialize (which observation makes you think that it overheats)?

  • Which part of the Proxmark device overheats (has unusual high temperature)?

  • Which firmware version?

  • Which Proxmark3 version?

Last edited by piwi (2018-08-03 18:30:15)

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#2 2018-07-31 10:30:34

piwi
Moderator
Registered: 2013-06-04
Posts: 524

Re: Poll: Is your Proxmark3 overheating?

I tried desperately to overheat my PM3 devices (one original board layout and one Elechouse RDV2) but failed miserably. See http://www.proxmark.org/forum/viewtopic.php?id=5506 for the test and the results.

Anyone experienced overheating of his/her Proxmark device? Or is it just a rumour or misunderstanding?

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#3 2018-07-31 13:41:04

AntiCat
Contributor
Registered: 2010-01-01
Posts: 14

Re: Poll: Is your Proxmark3 overheating?

For one of my current projects I've read trough the Pm3 Rev1 design: Schema

I've noticed a few special design choices. For the potential overheating issue, I would recommend looking at the coil drivers (IC9 and IC10).

They look like candidates for overheating. On page five you can clearly see that up to 4 independent* drivers are connected in parallel without any current limiting resistors (Up to 8 are connected with some current protection). Since there are always imperfections and tolerance that lead to switching delays and voltage offsets, there will be cross driver currents.

Addendum: Perhaps Pm3 Rev4 might have different drivers that are more sensitive to cross driver currents.

*The Datasheet does not mention any cross driver thermal coupling.

Last edited by AntiCat (2018-08-01 19:57:38)

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#4 2018-07-31 16:00:31

piwi
Moderator
Registered: 2013-06-04
Posts: 524

Re: Poll: Is your Proxmark3 overheating?

We are thinking along the same line. In fact IC10 became wamest (well, 34 degrees, which is virutally nothing) during my tests. And I thought about backdriving issues with parallel outputs as well. But the 74ACT line is extremely robust in this respect. From the data book "RCA Advanced CMOS Logic ICs - AC/ACT":

Output Short-Circuit Current (Backdriving)
Note that in Fig. 17 short-circuit currents of ±200 milliamperes are typical for AC/ACT outputs at a Vcc of five volts. Backdriving these outputs during PC board test by forcing outputs to ground, for example, is permissible with the limitations that only one output per IC be backdriven at any one time and for only one second maximum. For durations longer than one second, the IC may become too hot. Fortunately, because the epitaxial-based process is essentially latch free, no danger of latch-up results from backdriving.

Drivers of different chips (IC9 and IC10) are not connected directly but always with a current limiting Resistor.

The drivers with directly coupled outputs are from the same chip (therefore I would not call them "independent"). Variances of the propagation delay times between the drivers on a single chip are unlikely. But even if we would assume one driver with the minimum t_pd of 1.5ns and another driver with the maximum t_pd of 9ns on a single 74ACT244, there would only be 7.5ns (less rising/falling times) of backdriving at each edge of the 13.56MHz signal, i.e. only 20% of the total pulse width.

So I would conclude that overheating resulting from backdriving can be excluded with the known schematic and components.

Indeed it will be interesting to see the rdv40 schematic once it is published.

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#5 2018-08-01 18:25:07

piwi
Moderator
Registered: 2013-06-04
Posts: 524

Re: Poll: Is your Proxmark3 overheating?

@AntiCat: btw, your datasheet link is for a 74ABT244A, which is slightly different from the 74ACT244.

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#6 2018-08-01 19:58:05

AntiCat
Contributor
Registered: 2010-01-01
Posts: 14

Re: Poll: Is your Proxmark3 overheating?

Ups, I've fixed the link now.

(My only other idea would be a failed capacitor that shorts to ground. I don’t know if it's makes sense to keep guessing. Getting a failed unit to inspect would definitely help more.)

Last edited by AntiCat (2018-08-01 20:09:44)

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