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Author Topic: $50 Dollar Robot PCB  (Read 1630 times)

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Offline JdogTopic starter

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$50 Dollar Robot PCB
« on: March 25, 2009, 12:58:18 PM »
I just finished etching my PCB for the $50 robot board. It was my first time and there were two shorts. I decided to try and get rid of them by scraping away the copper connecting the traces together with a knife. I think it kind of worked, but when I was checking connectivity with my ohmmeter between the two previously connected traces, I'm getting really weird results. When I first touched the probes to the traces it flashes 130 kohm and then the resistance climbs to over 200 kohm, at which point it's too high for my meter to read and it goes blank. What's going on and if I have a resistance of 130000 ohms between power and ground would that be a problem?

Offline MrWizard

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Re: $50 Dollar Robot PCB
« Reply #1 on: March 25, 2009, 01:38:52 PM »
Can you be more specific ?   Where do you measure on the board ?
If you are measuring resistance also very high there might be another circuit route you are trying to measure.
 

Offline JdogTopic starter

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Re: $50 Dollar Robot PCB
« Reply #2 on: March 25, 2009, 01:44:47 PM »
Can you be more specific ?   Where do you measure on the board ?
If you are measuring resistance also very high there might be another circuit route you are trying to measure.
 

I have two copper traces right next to each other on the board. There is no components in yet, just the traces. They used to be touching in a small point so I cut away the copper connecting them with a knife. I put one probe on one trace and another on a different one.

Offline Soeren

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Re: $50 Dollar Robot PCB
« Reply #3 on: March 25, 2009, 06:33:31 PM »
Hi,

That's the kind of reading you would get from a capacitor.

Did you put a pinkie on the board while measuring?
Did you scrape a wide enough channel between the tracks, that you can clearly see light through it?
Did you rinse the board thoroughly, with lots of water and light scrubbing, with a soft dish washer brush or similar after etching?
Do you have any acid traps on the board?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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Offline JdogTopic starter

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Re: $50 Dollar Robot PCB
« Reply #4 on: March 25, 2009, 07:36:59 PM »
Hi,

That's the kind of reading you would get from a capacitor.

Did you put a pinkie on the board while measuring?
Did you scrape a wide enough channel between the tracks, that you can clearly see light through it?
Did you rinse the board thoroughly, with lots of water and light scrubbing, with a soft dish washer brush or similar after etching?
Do you have any acid traps on the board?

I realize that's the kind of reading from a capacitor but I don't have any components on the board. My pinkie was not on the board, I did scrape a wide enough channel, but I think there might be a tiny bit of copper connecting the two and that's why I'm getting these readings, but I can't get it off, although that should still give a constant resistance. I washed it heavily with acetone to get the ink off after I etched it, and lightly with water after that. I'm not quite sure what acid traps are but if it's just small puddles of acid leftover on the board then no I don't have them.

EDIT:
I just washed and cleaned off the board again, and now when I test it it's all good, so I guess there was a small copper flake or something like that connecting it.  :)
« Last Edit: March 25, 2009, 07:50:41 PM by Jdog »

 


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