Wi-Fi Stepper - CrowdSupply campaign is GO - Page 1
Forum section: electronics / general

author: aklofas
author_rank: Newbie
timestamp: January 24, 2019, 10:32:55 pm
content: Hello everybody!The Wi-Fi Stepper is a feature-packed stepper motor controller accessible over Wi-Fi. It supports up to 85 V input voltage, 10 A rms output, and max speed 4500 RPM. It can handle all stepper motors I've thrown at it so far (tested up to NEMA 42). The campaign is now live on Crowd Supply.https://www.crowdsupply.com/good-robotics/wi-fi-stepperLet me know what you think and if you have any questions! Attached are some glamour shots of the boardThanks!

author: beanflying
author_rank: Super Contributor
timestamp: January 24, 2019, 10:56:34 pm
content: While it is a nicely specced driver the WiFi control of what can be a fairly powerful motion system needs to come with proper cautions to any user.While I appreciate you can add mechanical interrupts for travel limits what if any power limiting or feedback is available from the driver in the event of a jam or say human getting caught in any motion device and what then happens? If a user leaves it with stock firmware and uses your web interface or app what is the default for a server or wifi failure?I am on your mailing list as of a few days ago and will most likely grab one for a play btw so I am not just picking on it but I do have some concerns depending on the implementation by unskilled users.

author: Mr. Scram
author_rank: Super Contributor
timestamp: January 24, 2019, 11:02:22 pm
content: Are there any safety features due to the nature of WIFI?

author: aklofas
author_rank: Newbie
timestamp: January 24, 2019, 11:23:43 pm
content: That's a great set of questions regarding safety features. To start out with, there overcurrent/voltage flags that can be configured to shut down the motor at arbitrary levels. So if, for example, the motor hits something and stalls (spike in voltage under "voltage mode"), it can detect it and shut off. This does need to be configured though and depends on the motor size.Additionally, there is a switch input that can be configured as a homing or e-stop switch. It's attached to a pull-up, so a number of switches can be connected in parallel and if any of them are grounded, it will enter hard-stop (active bridge) mode. The switch logic is built into the motor controller and is independent of the wifi chip (esp8266), and as such there is no latency and the stop is immediate.Finally, the wifi has a few safety features as well. While the web interface doesn't have auto-shutoff when disconnected (although maybe I *should* now that you mention it), the low level TCP and UDP connections that python uses do. There is a configurable heartbeat that will trigger a shutdown mode if there is a timeout. The idea is that, once you get the right configuration and motion commands figured out through the web interface, you'll most likely want to use python/etc. to integrate the motor commands into a larger application. That's where the "full power" of the security features (crypto chip) and safety features kick in.Does that satisfy the question? I could go into more depth if you like.

author: beanflying
author_rank: Super Contributor
timestamp: January 25, 2019, 01:07:34 am
content: Thanks for clarifying a few of the questions.I having a quick look at your bit bucket page and I didn't see any real documentation so I gather this is still a WIP? Implementing and well documented safety features for user written code should be clearly spelled out in particular.The few sonoffs I have in use have a 'power on state' to keep or not for example in the event of a power cycle and will ignore any loss in WiFi and keep doing what they need to independently of server or WiFi. Needed in particular as the Sonoff Server isn't always upMust get around to reflashing them with Tasmota or similar and loose ewelink.As you have some of the motion load protection issues covered is it worth having an option that on loss of wifi or a power cycle the stepper does X to a user defined position. Some of my thinking is that if these boards find there way into entry control of some sort as an example, WiFi loss or intentional jamming giving a simple auto shut off default is a security or potentially a safety issue (locked in) so auto off or keep default state option would be better than just default off on your web interface and sample code? As you mention possibly part of a larger system or custom code but it lends itself to simple standalone remote applications IMO using minimal user coding.

author: aklofas
author_rank: Newbie
timestamp: January 25, 2019, 04:08:51 am
content: Documentation is still a WIP at this point. There is some basic hookup/troubleshoot documentation in the web interface, but a standalone guide is in the works.Those are some excellent points regarding default safety modes, I'll be sure to add them to the software. At one point I was looking at embedding a lua interpreter (a la nodemcu) to give the board some editable autonomous/scripting behavior. I still really want to, but I don't think I have the time. If anyone on this forum knows how, I'm very friendly and will reward with free hardware

author: Kasper
author_rank: Frequent Contributor
timestamp: January 25, 2019, 07:11:04 am
content: Cool project. Nice job.Quote from: aklofas on January 25, 2019, 04:08:51 amOn a related note, some control4 drivers use lua so I imagine there are some home automation folks that would appreciate that.

author: Kasper
author_rank: Frequent Contributor
timestamp: January 25, 2019, 07:23:35 am
content: Quote from: aklofas on January 24, 2019, 11:23:43 pmWhat happens if there is a bad connection to the e-stop button?I've always been a fan of NC e-stop buttons that are wired such that if a wire or connection to the button breaks, it will act as if button was pressed.It would suck to have a connection fail and not know until you try to use the e-stop and it doesn't work.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 25, 2019, 07:09:35 pm
content: That's nice. What would be the applications of controlling a stepper motor wirelessly though? A whole robotic platform, I could envision that (although much care would have to be taken for safety reasons), but individual motors?Not willing to rain on your parade, just wondering.

author: aklofas
author_rank: Newbie
timestamp: January 25, 2019, 07:35:45 pm
content: This board isn't a complete solution for all applications. However, I think plenty of applications can get a use out of it. This motor controller is useful where a single motor is needed, such as pumps and dispensers. I have a 1-axis linear camera rail (w/ stepper) that I control with my phone. This controller board is perfect for that application as well. Home automation or anytime where you have a single motor way off somewhere and it's inconvenient/impractical to run wires.Additionally, you can connect multiple board together and control them through one interface. All commands have an optional 'target'. If you have a few boards wired together (through serial UART), one interface will control several motors. With this you can add extra axis or degrees of freedom fairly easily.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 27, 2019, 11:57:20 pm
content: Thanks for your answer. Your camera rail example seems relevant indeed.If your controller is chainable, then it answers my remark about controlling just one motor.Does it have two-way communication though?I think if your controller were able to send back data (such as from sensors, or conditions related to the motor itself such as overcurrent, which could be a sign of a mechanical issue), that would add definite value.

author: aklofas
author_rank: Newbie
timestamp: January 28, 2019, 01:00:16 am
content: Quote from: SiliconWizard on January 27, 2019, 11:57:20 pmThere is definitely 2-way communication. You can poll all the flags/position/speed/signal information from the motor. Additionally, there are some IO pins broken out that you can interact through the web interface: I2C, GPIO, ADC (12-bit), SPI, UART (depending on the mode), and the classic stepper driver step-clock drive. There is also E-Stop/homing external switch support (just wrote an update about this:https://www.crowdsupply.com/good-robotics/wi-fi-stepper/updates/homing).

author: aklofas
author_rank: Newbie
timestamp: January 28, 2019, 06:14:40 am
content: DroneBot Workshop reviewed the Wi-Fi Stepper about a week ago. It's a really thorough review posted here:

author: beanflying
author_rank: Super Contributor
timestamp: February 09, 2019, 12:09:20 am
content: Great to see the product evolving. EMI reduction, checking and tweaking of specs and a board revision. I finally added my lazy butt to your backers because of the updateAll of this and you look like meeting your timeline