21 August - PCBs arrived, some failures to report

A project log for IP control for inexpensive line following robots

A project for my grandchildren to first build line-following robots then convert them to being controlled by their phones and tablets.

jedjed 08/21/2019 at 20:540 Comments

The PCB boards from OSH Park arrived promptly, but I was out of town. I ordered 16 July and they arrived about 27 July, using only the free shipping option. I assembled one and everything went smoothly UNTIL I tried to use it. The components all fit properly and soldered easily. The boards were exactly as I tried to design them and a delight. A few dollars and a few days let me avoid the all the troubles of etching my own. Again showing that just because you CAN do it yourself does NOT mean that you SHOULD. The knowledge to do it also gives you the knowledge to understand when you shouldn't.

One change between the stripboard prototype and the PCB, that I mentioned in passing but didn't really explain, was the added jumpers. This picture shows the problem - different suppliers of the OLED displays have VCC and GND pins switched. The jumpers allow me to select which display I'll use this time.

My first problem with the PCB was that the display was flaky. That turned out that the components on the back of the display were touching the ESP8266 case beneath it. A strip of electrical tape quickly cured that.

The second problem is more difficult. Most UDP messages are NOT getting through. My first guess is that the display is now closer than in the stripboard prototype. The shorts requiring electrical tape showed that. Perhaps it is interfering with the WiFi reception by being so close. To test that, I need to mount the display higher with longer jumpers. I'll do that next and report here.

Another failure was in planning the assembly of the "tracking cars". I've found it takes about two hours of concentration for any of the inexperienced grandchildren to assemble a car and that's TOO LONG for some. It took even longer for the first ones, but I have a better procedure now. Also, I should have brought a VOM along to diagnose problems. One car had a joint so overheated that the traces around one lead broke on BOTH sides. I couldn't identify the problem without tools. That was poor planning.

 A positive thing was the weather. Our week together had perfect weather for being outside and ZERO days to be inside. That meant this inside project wasn't needed to fill a rainy day. Since it was NEVER a priority project for our week, that isn't much of a disapointment.

We ended our week together with three assembled cars, of which two worked correctly. They were assembled in the evenings by those most interested. The third car was fixed with a jumper wire across the two broken traces as soon as we got home.

We have postponed any races until our next get-together.

It's been very busy around here, so I'm behind on things - including updating this project. I'm trying to catch up.