Two peripherals attached to Q68 fried at the same time. Coincidence ?
Posted: Wed Mar 13, 2019 3:21 am
Hi,
As the title says, my Q68 setup sustained multiple casualties that appeared to take place at the same time.
The Q68 itself still work great. But I want to have expert opinions as to what might have happened and precautions I should take in the future.
Here is the setup:
Q68 powered by a HP-6623A lab regulated power supply. The Q68 is attached to a LCD screen and to a keyboard/trackball combo.
The HP-6623A also powers the LCD (12V) attached to its output #1
The Q68 is power by output #2 (5V)
The keyboard/trackball is attached to the Q68 through a KVM switch. (But the screen is directly attached i.e. not through the KVM switch)
I have been using the Q68 in this setup for a few weeks without problem.
A few days ago, after powering up everything, the Q68 boot process stops with the "No valid SDHC card found" message. A bit surprised (first time I see this) I power off the Q68, unplug/plug the card, retry and I get the same message. Try again after cleaning the contacts, same problem. Then I noticed the Q68 draw 0.450 Amps, it usually draws less than 0.200 Amps. With the card removed, the power consumption goes back to <200mA. The card was the one I received with the Q68.
As I wasn't sure if the problem was the Q68 or the card, I connected the card to a SD card reader and to my Mac, hopping the issue was with the card. As a matter of fact, the Mac didn't saw any new volume. After trying a few minutes, I removed the card from the reader and it is really HOT, like "burning your finger" hot.
I was quite surprised as I had no idea a SD card could become so hot. After reading on the internet, I realized this is an known issue with some SD card, some of them even catching fire. I guess this explain why the Q68 was drawing so much power, but probably even more current went through the card when it was plugged to the Mac.
I procured a new card and went through the process of re-installing SMSQE and WIN containers. (That is the only good point about the story. Now I know how to do this and I have learned a few things in the process). I lost all my Q68 configuration (no backup, I know, I know), but at least I did not loose any code as I backup my code on all my QLs).
I don't think "freaking hot SD cards" is a common problem, so I guess I was unlucky, but all in all not to big of a problem; I will do an even better SMSQ/E/application setup and this time I will do backups...
The new card booted without error messages and soon I was presented with the 3 windows and flashing cursor... only to find out that the keyboard did not work anymore. But the trackball worked. Removed the keyboard from the KVM switch: same problem. Try the keyboard to another computer: not working. Open the keyboard and checked the cable/plug continuity from the PCB to the pins: no issue.
Now, having a self destroying SD card, I can accept that. It happens from time to time it seems. Having a working keyboard that stop working, I can accept that also. But having the two happening at, it seems, the same time, I find it strange.
I can see four possibilities:
1 - Something went wrong with the power supply and it fried both components. (I did something differently this particular time, see below)
2 - The card decided to die and brought the keyboard with it. Why ? Current too high ????
3 - Something went wrong with the keyboard and the card died because of it. Very unlikely. But who knows.
4 - Pure coincidence, also very unlikely.
Now more details about the powering up procedure I used.
The lab power supply can operate in two modes
- Constant voltage, the current will adapt to the power requirement of the circuit.
- Constant current, the current is limited to a certain value, so the voltage adapt so V=RI is still true.
By default, for safety, the HP-6623A have a preset maximum current of 0.080Amps and a voltage of 0 volts
What I usually do when I use this power supply is:
- I first disable the output
- Then I key in the maximum current I want to allow. In the case of the Q68 I usually enter 2 Amps. This is high enough so the PSU won't operate in constant current mode.
- Then I key in the voltage, i.e. 5 volts.
- Then I re-enable the output.
This is, in my opinion, the safe way to do it. And it has been working for weeks.
But this particular time, I was careless, (though it should not have been a problem)
- Powered up the PSU
- I did not disable the output
- I keyed in the maximum voltage first i.e. 5 volts
The fact that the output was limited to the default 0.080 Amps, the applied voltage end up to be around 2.7 Volts. So the Q68 stayed silent. When I realized the problem, I set the maximum current to 2 Amps and the Q68 was brought to life... with the "No valid SDHC card found" message. You know the rest.
Now even though I did not followed my rigorous power up scheme, I find it hard to believe that 2.7 volts at 0.080Amps can destroy electronics designed to works at 5 volts. But I am no expert, this is why I ask.
As I said, the Q68 now works perfectly with another different keyboard and the new card. I did not tried yet to go trough the KVM switch (can that be the problem ??) I did not tried all Q68 features (i.e. serial port)
I did bought another keyboard combo, identical to the one that fried. But I am uneasy to plug it to the Q68, even though it is probably not the culprit. (This particular keyboard is quite expensive and difficult to come by, so I don't want to blow another one)
What is your views on this ? Reason 1, 2, 3 or 4 ?
Was I very lucky my Q68 survived ?
Peter will know the electrical path between SD card and keyboard and if one can bring down the other.
Or am I just very unlucky ??
Thank you for your time.
François
As the title says, my Q68 setup sustained multiple casualties that appeared to take place at the same time.
The Q68 itself still work great. But I want to have expert opinions as to what might have happened and precautions I should take in the future.
Here is the setup:
Q68 powered by a HP-6623A lab regulated power supply. The Q68 is attached to a LCD screen and to a keyboard/trackball combo.
The HP-6623A also powers the LCD (12V) attached to its output #1
The Q68 is power by output #2 (5V)
The keyboard/trackball is attached to the Q68 through a KVM switch. (But the screen is directly attached i.e. not through the KVM switch)
I have been using the Q68 in this setup for a few weeks without problem.
A few days ago, after powering up everything, the Q68 boot process stops with the "No valid SDHC card found" message. A bit surprised (first time I see this) I power off the Q68, unplug/plug the card, retry and I get the same message. Try again after cleaning the contacts, same problem. Then I noticed the Q68 draw 0.450 Amps, it usually draws less than 0.200 Amps. With the card removed, the power consumption goes back to <200mA. The card was the one I received with the Q68.
As I wasn't sure if the problem was the Q68 or the card, I connected the card to a SD card reader and to my Mac, hopping the issue was with the card. As a matter of fact, the Mac didn't saw any new volume. After trying a few minutes, I removed the card from the reader and it is really HOT, like "burning your finger" hot.
I was quite surprised as I had no idea a SD card could become so hot. After reading on the internet, I realized this is an known issue with some SD card, some of them even catching fire. I guess this explain why the Q68 was drawing so much power, but probably even more current went through the card when it was plugged to the Mac.
I procured a new card and went through the process of re-installing SMSQE and WIN containers. (That is the only good point about the story. Now I know how to do this and I have learned a few things in the process). I lost all my Q68 configuration (no backup, I know, I know), but at least I did not loose any code as I backup my code on all my QLs).
I don't think "freaking hot SD cards" is a common problem, so I guess I was unlucky, but all in all not to big of a problem; I will do an even better SMSQ/E/application setup and this time I will do backups...
The new card booted without error messages and soon I was presented with the 3 windows and flashing cursor... only to find out that the keyboard did not work anymore. But the trackball worked. Removed the keyboard from the KVM switch: same problem. Try the keyboard to another computer: not working. Open the keyboard and checked the cable/plug continuity from the PCB to the pins: no issue.
Now, having a self destroying SD card, I can accept that. It happens from time to time it seems. Having a working keyboard that stop working, I can accept that also. But having the two happening at, it seems, the same time, I find it strange.
I can see four possibilities:
1 - Something went wrong with the power supply and it fried both components. (I did something differently this particular time, see below)
2 - The card decided to die and brought the keyboard with it. Why ? Current too high ????
3 - Something went wrong with the keyboard and the card died because of it. Very unlikely. But who knows.
4 - Pure coincidence, also very unlikely.
Now more details about the powering up procedure I used.
The lab power supply can operate in two modes
- Constant voltage, the current will adapt to the power requirement of the circuit.
- Constant current, the current is limited to a certain value, so the voltage adapt so V=RI is still true.
By default, for safety, the HP-6623A have a preset maximum current of 0.080Amps and a voltage of 0 volts
What I usually do when I use this power supply is:
- I first disable the output
- Then I key in the maximum current I want to allow. In the case of the Q68 I usually enter 2 Amps. This is high enough so the PSU won't operate in constant current mode.
- Then I key in the voltage, i.e. 5 volts.
- Then I re-enable the output.
This is, in my opinion, the safe way to do it. And it has been working for weeks.
But this particular time, I was careless, (though it should not have been a problem)
- Powered up the PSU
- I did not disable the output
- I keyed in the maximum voltage first i.e. 5 volts
The fact that the output was limited to the default 0.080 Amps, the applied voltage end up to be around 2.7 Volts. So the Q68 stayed silent. When I realized the problem, I set the maximum current to 2 Amps and the Q68 was brought to life... with the "No valid SDHC card found" message. You know the rest.
Now even though I did not followed my rigorous power up scheme, I find it hard to believe that 2.7 volts at 0.080Amps can destroy electronics designed to works at 5 volts. But I am no expert, this is why I ask.
As I said, the Q68 now works perfectly with another different keyboard and the new card. I did not tried yet to go trough the KVM switch (can that be the problem ??) I did not tried all Q68 features (i.e. serial port)
I did bought another keyboard combo, identical to the one that fried. But I am uneasy to plug it to the Q68, even though it is probably not the culprit. (This particular keyboard is quite expensive and difficult to come by, so I don't want to blow another one)
What is your views on this ? Reason 1, 2, 3 or 4 ?
Was I very lucky my Q68 survived ?
Peter will know the electrical path between SD card and keyboard and if one can bring down the other.
Or am I just very unlucky ??
Thank you for your time.
François