Open polyatail opened 4 years ago
polyatail
commented
4 years ago | Item | Quantity | Cost/Item | Line Total |
|---|---|---|---|
| OSH Park PCB | 1 | $13 | $13 |
| DRV8825 | 5 | $2.65 | $13.25 |
| SN75176A | 1 | $0.93 | $0.93 |
| ATMega328P | 1 | $1.67 | $1.67 |
| LM3480IM4 | 1 | $0.58 | $0.58 |
| JST Connector (Stepper Motor) | 5 | $0.17 | $0.85 |
| 2-pin Terminal Block | 4 | $0.75 | $3.00 |
| 7-pin Terminal Block | 1 | $2.45 | $2.45 |
| SPST Power Switch | 1 | $0.75 | $0.75 |
Total: $36.48 per board
polyatail
commented
4 years ago Notes for Revision 2:
R4SLEEP and RESET pins on DRV to an ATmega pin so we can sleep the controllers. IT turns out 3.3V isn't available until the chip is on, so using that to set SLEEP to HIGH doesn't work. We can use the pins that were previously used for DIR.DIR to 3.3V since we only need a single direction for this project. We'll need to figure out what the wiring harness of the stepper motors looks like and then connect them to AOUT and BOUT accordingly to get the correct direction.
There are 200 letters in total: five rows of 40 characters. Each character is driven by a 5-wire unipolar stepper motor which will be run as a 4-wire bipolar stepper motor, leaving the center taps unconnected (and possibly cut). In addition, each character has an SPST switch which is triggered when a carousel reaches its "reset" position.
One of the PCBs for this project will drive five characters, and so there must be a total of 40 such boards. They must:
The BOM is going to be something like:
I think we probably need one 120V AC -> 12V DC power supply per 40 character rail, providing a total of 10A. That'll give them each about 3W of power while turning--that really should be enough!
Datasheets
28-BYJ48 (5-wire unipolar stepper motor) http://robocraft.ru/files/datasheet/28BYJ-48.pdf
A4988 (bipolar stepper motor driver) https://www.pololu.com/file/0J450/a4988_DMOS_microstepping_driver_with_translator.pdf
DRV8825 (another bipolar stepper motor driver) https://www.ti.com/lit/ds/symlink/drv8825.pdf https://www.pololu.com/file/0J603/drv8824-drv8825-stepper-motor-driver-carrier-schematic-diagram.pdf
SN75176A (RS485 transceiver) https://www.ti.com/lit/ds/symlink/sn75176a.pdf
B5B-XH-A-LF-SN (JST connector for stepper motor) https://www.digikey.com/product-detail/en/jst-sales-america-inc/B5B-XH-A-LF-SN/455-2270-ND/1530483
S8BYJ48 (stepper motor) https://components101.com/sites/default/files/component_datasheet/28byj48-step-motor-datasheet.pdf