I am almost done with my quadruped project. It’s spider-styled robot with 4 legs and 12 servos. I use RDS3115MG servos for this project, because they are very powerful and have nice mounting with fake dual shaft. They aren’t so expensive, $10 each.
I got 13 servos before assembling. I thought 1 spare servo is enough but 2 servos had burnt. The voltage was correct. Every servo has the same power suply, but only two burnt. The interesting thing is that when power was going to the servo nothing happens as expected. But when the pulse was applied to them, they started to smoke and one chip was going to be red.
As usual, I am waiting for another servo, my AliExpress seller sent me as replacement. Maybe there was some shorts. I don’t know…
I will post some pictures and description of the robot as soon as I will finish it.
I decided to use other E-ink display without third color
The display I wanted to use has 3 color – black, white and red, that sounds great, but it doesn’t support partial update and the fullscreen update is slow – 8 seconds. The new display I will use is the same but without red color, only black and white. It can be refreshed in just 2 seconds and the partial update is fast enough.
I searched for shops to buy that display. I found 2 versions of the same display. The first one from smart-prototyping looks thin. I don’t think so it’s thinner than the display from RLX. It has smaller bezels, but the RLX shop is located in my country, it’s cheaper and I can cut the borders of the PCB by myself with micro saw.
I am looking forward fastest updates, partial updates and RedBear board too.
There are several types of displays on the market: OLED, TFT, LCD and e-Paper displays. The biggest OLED display is 1.3″ 128×64, TFT touch screens are on the other side too big for my smartwatch project and they drain a lot of energy. LCD Nokia 5110 display is
great. I like it. The power consumption is below 1mA but the resolution is 84×48 and I’ve found that pixels aren’t squares but rectangles and a circle looks like an ellipse. LOL. I want to try these new type of display available now. So I choosed this E-paper display which I’ve mentioned about in the previous part. I measured the power consumtion, the thing what depends on, and the result is awesome. Just 0.02 mA when sleeping and 5mA when updating.
Yeah, the display works like so. You have to send whole buffer over SPI and then send command for refresh the display. I am unable to do this with BLEPad. I can partially render the text and send it over and over. Too restrictive. I have to save some RAM for notifications. One character = One byte. Not so much for storing the messages with a RAM of that size.
The winner is RedBear Lab Nano V2 which will be used in my smartwatch and I will call them just Red Bear to be short.
I first boughtBLEPad board which offers BLE module on the Lilypad style board with ATMega32u4. The BLE module was connected to the MCU via Serial1. It was easy to
make MCU sleeping and waking it up with external interrupt attached to the RX pin of the MCU. So I had to:
Send 1 byte to the BLE, the BLE sends it via Serial1 to the MCU
Detach interrupt and wake up the MCU
Wait 100 ms for clear next communication
Send my final message to the BLE which sends it to the MCU as well.
Why? Because interrupt attached to the RX pin of the MCU corrupts the Serial1 communication and I was unable to read the first byte correctly. I achieved 3 days of sleep time with this board.
I ordered successor of ESP8266 the ESP32. It features faster processor, more ram, more flash memory, WiFi. So I tried to do the same as with BLEPad and I wasn’t successful. The BLE support for Arduino ID
E was longer unavailable. I couldn’t make it sleeping and waking it up as the BLEPad could. I was surprised that using WiFi libs and BLE libs took over 113% of the flash. I was unable to turn off WiFi and use just BLE with interruption. Maybe I was wrong and it’s possible to do. I am using Arduino IDE because of simplicity and everyone can understand the code etc. The ESP32 with BLE used took more than 80mA of current. LOL.
It declares ultra low power consumption with BLE turned on. I got small chip for $2 from AliExpress. I didn’t know how to programm it and what software I have to use. I was new to the Nordic Semiconductors. I have worked only with Atmel of Espressif before. I needed a tutorial and got into it. However the RedBear Lab Nano V2 is here. The pricey board with exactly this chip. I will see what can $30 wrapped NRF52832 do.
I will compare specs of these board and explain why I choosed the last one.
Smartwatch is kind of nice accessory for you and your phone. You can see time, notifications without touching your phone. I wish I could have a smartwatch with long lasting battery and I could show the content I like. The very good one (I don’t mean Apple Watch) are expensive. So I decided to build my own smartwatch 9 month ago. It was a challange for me and my friend, who will build a better one. The research I did took some time.
This year’s Robocup Junior Competition was great. It was our second atempt on the world cup. We as team LiptovEffect were ready and successful I think. At the begining of working on new robot we were scared of lasers. They were shuting down randomly and we coudln’t find out why. But what can you expect from a robot built in 2 weeks?
We won the Superteam challange of the Rescue Maze competition and we achieved 3rd place in Rescue Maze Individuals. What is Superteam Challange? When the individual competition was done, a team was randolny matched with other team and they were working together. We got new task and had to find solution. Team from China, we were in Superteam with, was 2nd in individuals. So it wasn’t so hard to make things working again.