One checklist to run on any robot part before you pay. It works for motors, drivers, sensors, batteries, boards and kits. It contains no prices and no brand recommendations. Compare current listings yourself.
Before you search
- Write down what the part must do and the numbers that matter: voltage, current, speed, torque, range or resolution.
- Decide your supply voltage and logic voltage first, so you can filter parts that do not fit.
- Write your budget as a range and leave room for spares.
Read the listing
- Is there a datasheet or a clear specification table, not just marketing words?
- Do the rated voltage and current cover your use with a margin?
- Is the interface stated (I2C, SPI, UART, PWM, analogue)?
- Are the pin names and connector type shown in a photo or diagram?
- Are example code or libraries linked, and do they match your board?
Check the seller
- Seller rating, return window and who pays return shipping.
- Whether the item is new, used or a clone, and whether the listing says so.
- Delivery time, and whether you can wait if the part is out of stock.
- Whether you get a proper invoice.
When it arrives
- Photograph the parcel and the part before use.
- Check the markings match the listing.
- Test on the bench with a current-limited supply before fitting it into the robot.
- Keep the invoice and listing screenshot until the return window ends.
For planning a full build use the project cost calculator. Keep notes in the bill of materials template. All current buying guides are in the buying guides category, and the Learn hub explains the ideas behind the specifications.
Last reviewed: November 2026. Free to copy and adapt for your own project, with credit. Written, checked and maintained by Jignesh Panchal of Jaadu Digital. See the editorial standard.
How to read the numbers
- Rated voltage and current: pick parts whose continuous rating is above what you need. For a motor driver, compare its continuous current with the motor’s stall current, because stall draws the most. If a motor stalls at 1.2 A, a driver rated for 2 A continuous gives about 1.7 times margin.
- Peak and continuous are different. A battery or driver listing may quote a short burst, so look for the continuous figure.
- Capacity: a 2,000 mAh battery supplying 500 mA lasts about 4 hours in the ideal case, and less in practice. Use the battery runtime calculator.
- Logic level: a 3.3 V board needs a part that accepts a 3.3 V signal or a level shifter.
Signs of a poor listing
- No datasheet and no part number, only a brand-like name.
- Capacity or power claims that look far above similar parts at a similar size.
- Photos that do not match the title, or different photos in each review.
- No contact details or return policy.
A short example of using the checklist
Say you need a driver for two small motors that stall at 1.2 A each. Write the requirement first: 2 channels, at least 2 A continuous each, motor supply of 7.4 V, 3.3 V logic. Then filter listings by those numbers, check the datasheet for the voltage drop, and note whether the pins are labelled in the photo. Compare two or three candidates in a small table, and keep your notes for the bill of materials.
Before you click buy
Check the total including shipping and tax, the delivery date and the return window. If a part is for a deadline, order spares of cheap parts that fail easily.