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Author Topic: DIY perf board shield  (Read 1650 times)
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I have two waterproof CDS sensors reading LED output in a vat of pulp that will determine the weight of hand made paper by reading density between the two. The CDS is reading fine on the serial monitor but the LED's are barely lighting even though the voltage is just over 5v on the perf board rails.  In another configuration (no shield), the system worked fine powered by the Arduino.  I assume an error in the DIY shield has radically compromised current?  Any ideas?
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Sorry, the link didn't make it in the first post. http://www.flickr.com/photos/50454200@N06/8075405682/

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Dubuque, Iowa, USA
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Did you remember to pinMode(ledpin, OUTPUT);?
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Yes, pinMode is set to output. The LED's are lighting, just barely visible. Same sketch was lighting them brightly previous to the shield setup.
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Valencia, Spain
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the LED's are barely lighting even though the voltage is just over 5v on the perf board rails. 

What's the voltage at the LEDs? Have you got correct resistors? Try replacing the LEDs.

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Voltage at the LED is just over 5v.  An LED at the 5v/gnd connections from the Arduino isn't bright either, even without a resistor!
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Valencia, Spain
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Voltage at the LED is just over 5v.  An LED at the 5v/gnd connections from the Arduino isn't bright either, even without a resistor!

Damaged LEDs...? Try a different one.
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Quick, chuck it in the bin before the boss finds out...
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Anything getting warm suggesting a short somewhere?
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Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

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Nothing warm and checked LED's with same resistor. They are bright. Seems odd. Can't understand why the
LED's are so dim on 5v.
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Thanks for the advise. Taking the cowardly way out; going to Radio Shack for a shield. This is my fourth time around with perf board with no guarantee the next attempt will be successful.
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Did you verify that ground on the shield was ground?. Frequently the assumption is that "Ground is Ground"... Having the correct voltage on one side is no proof that the other side is correct. If your ground return is the culprit... Always measure across the part as a means of separating bad parts from bad wiring.

Bob
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Voltage at the LED is just over 5v.  An LED at the 5v/gnd connections from the Arduino isn't bright either, even without a resistor!

What I meant was: What's the voltage between the legs of the LED when it's lit up?
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how are you powering this? maybe if using a USB, then you can try external power supply?
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For unknown reasons, the shield is working as designed. Little afraid the short may reappear but satisfied for now.  Thanks.
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From the information you reported it is more likely an intermittent ground return to the Uno than a short. Shorts usually draw great amounts of un wanted current. It's also possible that your ground is/was a port pin that was providing the ground. Somewhat appropriate was an incident in the aerospace industry that I was a part of as a consultant, I didn't find or fix the issue but I was there when it was. a designer built a rather big PCB (about 60 Cmos IC's) and it worked well except at rated clock speed and the issue turned out to be the main 5V source lead... not soldered properly on a shrouded connector. Seems that the inputs from outside control elements were powering the board, through the input protection diodes.

Bob
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