DC setup frying computers.

Thread Starter

madu268

Joined Feb 13, 2021
5
Hello

Can someone please be so kind and take a look at my setups and guide me in a better direction.
I've managed to fry already 2 computers without understanding the cause of it.
I gave my best to visualize the setup. Both times it has also fried the USB to RS232 coverter. Everything else seems to remain functional and undamaged.
Prior to connecting I have tripple checked the polarities and voltages and everything has been in order.
I have had no problems by running the optiplex on 19.5v with stepdown buck from the 24v battery source for many weeks straight. Right after connecting the touchscreen the pc was dead in 5-10 sec. Is the problem here trying to combine 12v and 24v power sources together in such way?
Thanks in advance!

Setup 2.jpg

Setup 1.jpg
 
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Deleted member 440916

Joined Dec 31, 1969
0
Looks to me like you have some unintentional power return current flowing through your USB & RS232 grounds. This is most likely caused by poor bonding in your main power path, loose connections, inadequate wire gauge or connections to long. I have had nasty surprises using USB oscilloscopes with laptops so now I always remove the power adapter and run on internal batteries whenever in doubt, works a treat, I suggest you do the same while you sort things out.
 

BobTPH

Joined Jun 5, 2013
3,315
And I would say I cannot make sense of your diagrams.

You have one battery with 2 red and 2 blue lines coming out of it. Perhaps this means two connections to B- and two connections to B+.

But what about the other battery that has 2 red lines only out of it? What am I to make of that?

Bob
 

Thread Starter

madu268

Joined Feb 13, 2021
5
hi mdu,
I would say that the USB to RS232 link is grounded at both ends thus shorting out the top 12V battery.
E
Thanks for a quick reply, and what would you suggest doing?
Since I didn't have any problems with just the pc and rs232 connection using the 24V supply, i'm considering just stepping it down twice (19,5v for pc and 12v for the needed screen). My initial thought was that it would be easier to get the needed 12v straight from one of the batteries.

Also if this theory is true has anyone any idea about the extent of damage to the computers?
 

Thread Starter

madu268

Joined Feb 13, 2021
5
And I would say I cannot make sense of your diagrams.

You have one battery with 2 red and 2 blue lines coming out of it. Perhaps this means two connections to B- and two connections to B+.

But what about the other battery that has 2 red lines only out of it? What am I to make of that?

Bob
Hey
Just made some quick illustrations and i'm no electric specialist. As you can see from the devices connected, some of them take 24V and some 12V. Those 2 12v batteries are connected in series. Idk how to make it more clearer, i think some guys here figured it out already.
 

BobaMosfet

Joined Jul 1, 2009
1,776
Hey
Just made some quick illustrations and i'm no electric specialist. As you can see from the devices connected, some of them take 24V and some 12V. Those 2 12v batteries are connected in series. Idk how to make it more clearer, i think some guys here figured it out already.
You're making an excuse to be lazy. The fact that you are building a robot suggests you should already be familiar with how to create BASIC schematics. If you're not, LEARN how. It's like trying to speak to anyone- you need to do so in their language- at least try. If you're serious about your endeavor, _BE SERIOUS ABOUT IT_. :p

Good luck.
 

michael8

Joined Jan 11, 2015
137
What does that stepdown buck for the touch screen look like?

I'm thinking that a stepdown buck doesn't need to have the input and output negative directly connected -- the stepdown circuit
could be in the negative line...
 

Thread Starter

madu268

Joined Feb 13, 2021
5
You're making an excuse to be lazy. The fact that you are building a robot suggests you should already be familiar with how to create BASIC schematics. If you're not, LEARN how. It's like trying to speak to anyone- you need to do so in their language- at least try. If you're serious about your endeavor, _BE SERIOUS ABOUT IT_. :p

Good luck.
I am just trying to replace a proken pc and a touchscreen on an already built robot that needs to be running asap, so I am not being lazy. I am just looking for help from experienced people. If you don't want to or can't provide any assistance, no problem but I would appreciate if you kept my thread on topic and CAPS somewhere else.:)
 

djsfantasi

Joined Apr 11, 2010
7,693
The caps suggest an issue with your approach that may be the source of your problem and preventing you from resolving it. If you are distressed by the comment, you may not be in a position to learn from your mistakes.

You can ignore me if you wish. I won’t mind.
 

MisterBill2

Joined Jan 23, 2018
8,760
A simple fix will be to power that touch screen from a separate ISOLATED supply, totally separate from the computer power supply. Since there is no information about the separation of supply voltages from the interconnect wiring my guess is that there is a hidden connection that has caused the problem. Thus totall isolation of power connections is in order.
 
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