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Zac280

LED panel tester

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I'm looking for ideas on how to go about building a test device for an LED digit panel. The project is for a company that manufactures scoreboards so there are different types of digits and characters that need to be tested. The company orders the boards from another company where they are printed and installed with all the components. Sometimes some of the LEDs are shorted and a faulty board is installed. The tester used currently lights each of the 7 segments in sequence, while the operator must stare at each segment to be sure all the LEDs light. A better tester would allow the board to simply be plugged in and immediately notify the operator if the board is good or not.

One option for the new tester would include measuring the current draw of each segment to test for shorted LEDs. Measuring currents can be a tricky thing, however. Another option would be some sort of camera or light-sensing devices. The problem here is that the variety of boards would make the device very hard to configure to accomodate each of them. Also, this option would be more expensive.

I'm leaning towards some way to test the current in the panel, but I'm sure it would need to be very precise. Since each of the 7 segments can be accessed invidually, this may be feasible. The operator could adjust the test device to the type of panel being tested to adjust the current target.

What are some suggestions for such a scheme? Are there any other test options I should consider?

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The current monitoring I think is better and not so difficult. You must measure the voltage drop across the led current limiting resistor. If this voltage is over a user selected maximum level, an alarm is generated.

The circuit could consist of an opamp with adjustable offset

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tnk2k has a good suggestion. Most manufactured equipment has such a power up mode where all segments light when the device first comes on or a button to hold in to see all segments light up as a test. It sounds like the problem is more about the time to go through the test and not necessarily the test itself. There is no reason to light up each segment one at a time and wait. Light them all up at once and go on... This will be the easiest solution and will take the least amount of labor time.

Now, if the reason for this slow test was to see if the program was sending the correct numbers or characters, then you have a different matter.

MP

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