It's been less than a day since I last posted about my robot dog project, but I have a little update today that I want to talk about, because it's important. After going through the parts list that I worked out together with Claude, I finally decided to make the purchase order. It's a pretty big order, around $900 and roughly 30 items.
I had a few things already, such as a multimeter and a luggage scale, but for the most part I'm going to be using all new tools, because frankly I didn't have that much to begin with. So things like a soldering iron and wire clippers are in there, and there's a bunch of little parts like capacitors and resistors. But really the big bulk is the two servos. There's one for the knee, which is the more expensive, more powerful one, and then one for the hip. This is not even enough to make one leg, but it is enough to measure the servos' capacity and start understanding how to use them. I'm also ordering something called a Teensy, which is going to be used to help drive those servos and control them.
So I've got a lot on my hands to work with as soon as these start coming in. I'm going to take it in baby steps. That's one great thing about this project. I don't have to commit to the full $6,000 or $7,000 build. I can just go little by little. This will probably give me enough to work on for maybe a few weeks. We'll see how quickly I'm able to make progress.
If I do make good progress with this, the next step will be to start making some leg parts so I can actually start building a leg, and buy one more servo. There's a big question there. Do I start ordering these parts via 3D printing from an outside source, or do I buy my own 3D printer? The 3D printer that I want is not exactly inexpensive. I think it was around $700. But I have a lot of options, and this sounds like a really fun project, so I'm looking forward to it.
I'm going to go ahead and paste the entire parts list of what I bought. I'm not suggesting that anyone tries this with me yet, because it's very early stages. I may need to rebuy things, or I may break things, or find out that things are wrong. Although I am doing a check of everything before I buy, it's possible there can be mistakes.
The parts
Everything below came to $921. Prices are rounded to the dollar.
The two motors ($450)
| Part | What it's for | Price |
|---|---|---|
| RobStride 06 actuator | The knee motor. 36 N·m peak, with the motor, gearbox, driver electronics and position sensors all in one 621 g can. It takes the biggest loads in a jump, so it's the one to test for heat first. | $260 |
| RobStride 02 actuator | The hip motor, also used for the side-to-side joint. 17 N·m peak, 405 g. The dual-encoder version knows its output position at power-on, which the robot needs to stand up safely. | $190 |
Power and wiring ($141)
| Part | What it's for | Price |
|---|---|---|
| Bench power supply, 0 to 60 V, 5 A | Stands in for the batteries during testing. I can dial in 48 V and set a current limit, so a wiring mistake trips the limit instead of melting something. | $66 |
| USB-to-CAN adapter | Lets the Mac talk to the motors over their CAN bus. Also the official way to update motor firmware. | $25 |
| Motor cable, 3 m, plug to bare wires | Plugs into the motor. Two thick wires carry power, two thin ones carry data. | $24 |
| Spare motor plugs, pack of 10 | One becomes the bus terminator (a resistor in a plug). Two more make a jumper so both motors run on the same bus. | $10 |
| 16 AWG silicone wire | Wire for that jumper. | $8 |
| Capacitors, 1000 µF | Sit across the supply to absorb the voltage spikes a motor makes when it brakes. | $8 |
The Teensy kit ($108)
| Part | What it's for | Price |
|---|---|---|
| Teensy 4.1 | The microcontroller that will run the motor loop. It has three CAN ports built in. Bought with the pins pre-soldered. | $43 |
| CAN transceiver boards, pack of 3 | Translate the Teensy's signals onto the two-wire CAN bus. Two are used, one is a spare. | $8 |
| Breadboards | Plug-in prototyping boards, no soldering needed for the wiring. | $10 |
| Jumper wires | Short wires with pins on the ends, for the breadboard. | $7 |
| Resistor assortment | The 120 Ω resistors that terminate the CAN bus. | $9 |
| Micro-USB cable and USB-C adapter | Mac to Teensy. | $14 |
| USB isolator | Sits between the Mac and the bench. If 48 V ever gets where it shouldn't, this takes the hit instead of the Mac's USB port. | $17 |
Soldering tools ($151)
| Part | What it's for | Price |
|---|---|---|
| Pinecil soldering iron and a 100 W USB-C charger | The iron. It runs off a laptop-style charger and heats in seconds. | $77 |
| Solder, flux and desoldering wick | Solder is the metal that joins the wires. Flux helps it flow. Wick fixes mistakes. | $18 |
| Silicone mat and helping hands | A heat-proof work surface and a clip stand that holds small parts. | $18 |
| Heat-shrink tubing kit | Insulates finished joints. | $8 |
| Wire stripper and flush cutters | Clean insulation strips and close trimming. | $22 |
| Safety glasses, two pairs | One each for me and my son. | $8 |
Mount and test gear ($71)
| Part | What it's for | Price |
|---|---|---|
| Metric screw kit, M3 to M6 | Bolts the motor to its mount and the test lever to the motor's output. | $23 |
| Digital calipers | Measuring the motors' bolt circles and thread depth so the printed mount fits. | $16 |
| C-clamps, two | Hold the motor mount to the edge of the table. | $13 |
| Extension spring kit | A spring on the lever lets the motor move a little during the heat test, so the heat spreads over all three windings. | $10 |
| Paracord | Cord between the lever and a scale for the torque test. | $9 |