README.md 2.13 KB
Newer Older
Jake Read's avatar
Jake Read committed
1
2
## Stepper Module

Jake Read's avatar
Jake Read committed
3
4
[DEV LOG](log/ucbus-stepper-log.md)

Jake Read's avatar
Jake Read committed
5
6
7
8
9
10
11
These are stepper drivers! They run:

- ATSAMD51 Microcontrollers  
- 2x A4950 H-Bridges on 2x DACs to VREF
- 1x AS5147 if you want to get closed-loop-fancy  
- RS485 input and 40W 24V into one 10-pin IDC  

12
13
14
15
16
17
18
19
20
21
22
23
To build one w/ a motor, for closed loop stepping, I do:

- N17 Motor 17HS19-2004S1
- IDC, Plug, 2x15 609-5106-ND 
- IDC, Plug, 2x5 609-1746-ND
- Magnet 469-1076-ND
- Spacer 6mm Tall 94669A101
- M3 SHCS 50mm 91292A026
- DIP Switch 219-8LPSTRF
- 2x5 Latching 732-2679-ND
- Two Part Epoxy

Jake Read's avatar
Jake Read committed
24
25
The hardware is set up to run on the 'UCBus', a synchronous embedded protocol that establishes a bus clock *and* data lines on one RS485/UART Phy. Details are not documented anywhere ATM, but it w o r k s. 

Jake Read's avatar
Jake Read committed
26
27
28
29
30
31
## Closed Loop

Circuits have a land for an AS5147P encoder, with which they can run closed-loop stepper control:

![cl](log/2021-02-25_cl-step-perf.mp4)

Jake Read's avatar
Jake Read committed
32
33
34
## Melted Version V02

I revisioned this recently to skip the module and just build the whole circuit on one board. Schematic is identical to V01, but now is much smaller (can fit on a NEMA14 size motor) and all components are SMT on one side, i.e. the AS5047P is on the same side as the H-Bridges, Micro etc. 
Jake Read's avatar
Jake Read committed
35

Jake Read's avatar
Jake Read committed
36
37
38
39
40
41
42
43
44
45
46
47
The IDC UCBus connector & DIP Switch are on the flipped surface. 

![schem](log/2020-08-25_schematic.png)
![routed](log/2020-08-25_routed.png)

140 of these are out fab / assembly.

## Module Version V01

Beneath [the module](https://gitlab.cba.mit.edu/jakeread/ucbus-module).

Networked step driver (or) general purpose 2-H-Bridge ute. Uses module for micro / network drivers, all other parts are 0805 or similar to hand-solder easily. 
Jake Read's avatar
Jake Read committed
48
49

![fab](log/2020-07-28_ucbus-stepper-fab.jpg)
Jake Read's avatar
image    
Jake Read committed
50
![routed](log/2020-06-29_routed.png)
Jake Read's avatar
Jake Read committed
51
52
53
54
55
56
57
58
59
60
![schematic](log/2020-06-29_schematic.png)

## Voltages / VREFs etc 

The A4950 VREFs are hooked up to DAC0 and DAC1. 

Current limiting will be set by:

`Imax = Vref / (10 * Rs) ``

Jake Read's avatar
Jake Read committed
61
Where Rs is the sense resistor value, in this circuit its 0.2 ohms. So maximum current is 1.65A at 3.3v full DAC, all else scales. I think I set it up this way in case I was unable to set the DACs up properly, and had to turn them on full all the time.