Skoobot

I think the comparator is not going to switch without much higher offset voltage. I simulated it in LTSpice (free download, but only has Linear Semiconductor parts in it). The mistake is not fatal, I put in a manual override it case it failed. It's a good example of how it is a royal pain to check every little thing, but it can bite later. 

I went to the craft store and bought a better exacto. I bought some Sculpteo and made these creatures. I will now bake them in my reflow oven and see if it is like using a kiln. This has absolutely nothing to do with anything or even Tiny Robots.

I found a mistake, the Microchip MCP72832 Lipo charger I put in is different in a way I didn't expect. The status pin is open drain. On the MCP72831 I was using before it is tristate. The charging led would not light. I flipped the led around, then I flipped the resistor 90 degrees, then I solder that to 5V. It lit up and charging works fine. Here is a photo of the rework.

I also noticed the female connector bends back plugging in if I am not careful. I coudl glue it or some redesign. I put a 1k pot on power to simulate a load, and the comparator doesn't trip to UART. Although at 23.5 ohms (3V/23.5=127mA) the UART Tx and Rx leds light up. I had wanted it to switch to UART mode when sourcing current. Have to figure this out.

For the laser cut wheels, here i what they look like. I sandwich 3 of the cutouts together. They smell like burnt wood all the time.

Here are the tires (o-rings). I got black (called Buna) and Silicone (red) to which is stickier. Silicone is softer and stickier, but red might look funny. I actually learning somethings about Durometer, 50D is softer than 70D (the hardness measure).

It kind of took all day and I need a break. But here it is. The companion board has these features:

• USB to UART
  
  • UART or Arduino
• Robot power switch is Off
  • Arduino/UART mode
• Robot power switch is On
  • J-Link mode (C programming)
• Battery charging when USB plugged in
• USB 5V present red led
• UART mode green led, off in J-Link mode
• UART Tx and Rx led's
• Charging blue status led

It uses a FT323RL chip so is Arduino compatible, no dongle needed. Plus UART is nice for C debugging. I tested charging and J-Link, works great. When the new robot boards arrive I'll test UART/Arduino.

Just sent this robot body, the motor mount, and solderpaste frames, off to Sculpteo to get them printed. They don't do colors as easy as Shapeways, but Shapeways was saying 28 days for delivery, yikes! Sculpteo is about 60 miles away from me, so really close. I think Shapeways is in NYC. (Shapeways is cheaper though). In this design I put a slot for the buzzer to fit in the top. I really need an open sound path and hopefully resonance with the body for volume.

1. It's kind of weird, but the Android Studio BLE GATT example won't find Tiny Robot, but the Nordic nRF Connect will. I can try and make the example work, or use the Nordic library (no app source). I don't want to go down a rat hole with either one, but I don't want to start from scratch. Tough choice.

2. Parts and PCB's for companion board (programmer, UART, charger) show up Thursday. Pretty exciting.

3. Went to an Edtech meetup tonight and got some good advice on using the robot in schools. Like telling me little kids will stomp on it, or try and pull it apart (heard this from the voice of experience).

4. I costed out the robot, and it comes to $100 in parts (before labor). Obviously this is no good and it kind of bums me out, even though I kinda knew it wasn't going to be great. I regret not being aggressive on cost from the start. I have many ideas for getting the cost down though.

5. I gave the Shenzhen motor company a good review on Alibaba. 

Got a Moto E4 Android cellphone at Walmart to use as Bluetooth client for robot. Now I will write some apps.

I name this project "Project Johnson", then I realized my brother John has a son, that I think is great guy. Is this subconscious mind at work? (queue creepy music)