When you are making products in batches, you need a quick way to test them and make sure they function as expected. For example, three weeks ago, I sold close to 100 AASaver kits in a day, and I needed a good way to automate the testing before they are shipped out:
Well, this is what pogo pins are good for. So what is a pogo pin? It’s basically a spring-loaded pin that you can use to make a secure and temporary contact with your circuit board. It allows you to stack the testing circuit directly onto the target circuit, without any additional soldering. The picture on the right above shows an example I got from eBay. This is of model number P75-E, which is 1.02mm in diameter and 16.5mm in length, perfect for the AASaver circuit board.
To build a tester, I need to: 1) provide input power to the target board; 2) test the output voltages (5V/3.3V); and 3) test the output current (>300mA). These can be done by making use of an existing AASaver PCB. I used a total of 5 pogo pins. Two are soldered into the battery holes to provide input power from two AA batteires; two are soldered into the Vcc and Gnd, and further connected to a mini voltage meter for testing output voltages; and one more to provide weight balance. See the pictures below.
To use the tester, I simply stack it onto a target board, and check the voltage readings. Each test can be done in less than 8-10 seconds. To test the output current, I added a 15 Ohm power resistor and a slide switch onto the testing circuit. When the switch is turned on, the power resistor is applied between Vcc and Gnd, which causes an output voltage to drop. This drop should be relatively small (<0.3V) if the target board meets the current rating (>300mA). So there you go: a simple tester for the AASaver!
Did you test all 100 boards? What was your yield?
Yes, all boards were tested before shipping. I would say the yield was about 85-90%. The failed ones were typically due to reflowing glitches and were all easy to fix with a soldering iron.