Laika Explorer Board for Pi

Question

Evening all you lovely people, I'm doing a tiny bit of research here and I'm hoping someone can assist.

I'm looking at building an electronic vehicle dashboard, the initial part being stepper motor speedometer and revolution counter.

From my limited understanding of stepper motors they need a H-Bridge motor drive.

The Laika seems a possibility for a development board, it has analogue inputs (great for speed & RPM inputs) plus a few extra niceties and drops onto my Pi rather well (or it would if I had one - a Laika that is, not a Pi)!

Questions are:

1. Has anyone used (and can recommend -or otherwise) the Laika Explorer board? (Current CPC price circa £24 inc vat)

2. Am I correct in thinking that the dual H-Bridge will only drive 1 stepper motor?

3. Would something like the '4TRONIX PISTEP Stepper Motor Control Board for Raspberry Pi, or 'ADAFRUIT INDUSTRIES 2348 DC Stepper Motor HAT for Raspberry Pi Model A+, B+ or Raspberry Pi 2' (or similar) be a better choice? (Around £12 and £23 respectively).

The steppers I'm aiming to use are X27-168 (Sold by adafruit among others) -Adafruit Product code for reference 2424

"step precision of about 1/2 a degree per step, 600 steps for single stepping, fast response for quick movements, and a range of ~315° degrees".

Fingers crossed for some positive feedback / advice, then I can get buying more stuff that I might even get around to using!!

shabaz · Accepted Answer

I think I've found the ideal part : ) Check out this stepper driver IC stepper driver IC from On Semi. It runs from 2.5V to 16V, and can be controlled from 3.3V or 5V logic. You'd need two of them if you want to control two stepper motors, but these ICs are small and cheap. The size is non-standard (1mm spaced pins) but totally hand-solderable if you're prepared to build your own PCB. Everything is integrated so apart from a few capacitors it costs £1 per stepper.

shabaz · Answer

Hi Andrew,

A dual H-bridge will only control one bipolar stepper motor as you say. And ordinarily a dedicated stepper driver is preferred than just a dual H-bridge and no stepper driver.

However, those dashboard steppers are very low current, so personally I wouldn't use any stepper motor hat.. You could use just logic buffers to drive the stepper provided you are ok with coding

the stepper algorithm rather than having a pulse and direction control like some dedicated stepper driver ICs. Each logic buffer output would be a half bridge basically.

So, an option would be to parallel normal logic gates (e.g. AND gates with their inputs tied together, or hex/octal buffer chips, so that you can drive the motors with 5V up to 20mA or so.

Or, use something like 74ACT541 (power it from 5V) which has high current output so doesn't need additional paralleling, and it is an octal chip so it could control two stepper motors. It will accept 3.3V logic

inputs. So, this would be a single-chip solution to driving two of the motors.

It is SMD only but there are plenty of SMD breakout boards, and they are no more difficult than through-hole.

Also you'll need flyback diodes BAT81S is good enough if you prefer through-hole. Personally I'd go with the surface mount BAT54 range (there are different suffixes) since they have dual-diode versions, to

reduce the amount of discrete parts.