Search found 10 matches

by cyberdemon
Wed Oct 17, 2018 6:16 am
Forum: Velocity and Position Control
Topic: Safety stop on loss of Serial Connection
Replies: 13
Views: 9709

Re: Safety stop on loss of Serial Connection

Hello again :?

Any update on this?
by cyberdemon
Mon Jun 25, 2018 9:43 am
Forum: General Discussion
Topic: Questions about the safety wirings
Replies: 6
Views: 4885

Re: Questions about the safety wirings

nschoe, the reason the pre-charge resistor doesn't fry is due to voltage drop. In order to drive 5A through a 220Ohm resistor, you would need 1100 Volts (!). Since your battery can only supply (say) 24V, then a maximum of 0.11A can flow through your resistor, dissipating 2.4W (which is still quite a...
by cyberdemon
Mon Jun 25, 2018 9:31 am
Forum: General Discussion
Topic: Emergency Stop Circuit
Replies: 9
Views: 4646

Re: Emergency Stop Circuit

Hi Chris, While the ROS node has a watchdog function that will stop the roboclaw when it stops getting messages on its topic, it still has to send a command to do that. So if the serial/USB comms are broken between the roboclaw and the host PC, it will continue executing its last command forever. So...
by cyberdemon
Tue May 29, 2018 9:58 am
Forum: General Discussion
Topic: Emergency Stop Circuit
Replies: 9
Views: 4646

Re: Emergency Stop Circuit

Looks good although I suspect the 2n222 won't have a high-enough gain (hfe) which is why the original circuit used a mosfet. Unless you have a really low power reed relay I suppose.
Have you tried simulating it? "simetrix" is a useful program for this.
by cyberdemon
Tue May 29, 2018 9:16 am
Forum: General Discussion
Topic: Emergency Stop Circuit
Replies: 9
Views: 4646

Re: Emergency Stop Circuit

Hello, My solution for this was to make a hardware watchdog out of an "Arduino Pro Micro" and a power mosfet driving a pair of large automotive relays. The code is fairly simple; it waits for a character on the USB COM Port which switches on the relay and resets a timer. An interrupt routine increme...
by cyberdemon
Tue May 29, 2018 9:03 am
Forum: Velocity and Position Control
Topic: Safety stop on loss of Serial Connection
Replies: 13
Views: 9709

Re: Safety stop on loss of Serial Connection

Hello again :)

Any update on this?
by cyberdemon
Sun Jan 21, 2018 4:13 pm
Forum: General Discussion
Topic: Current flowing from roboclaw to RPi?
Replies: 3
Views: 2963

Re: Current flowing from roboclaw to RPi?

The USB ground on the RoboClaw is connected to the main battery ground. This can cause problems with ground loops in my experience, if the RPi is powered from the same battery as the RoboClaw (I have blown up one RPi the same way as you). I recommend these USB opto-isolators to avoid ground loops: h...
by cyberdemon
Tue Nov 21, 2017 2:06 pm
Forum: Velocity and Position Control
Topic: Reversing directions at limits (Roboclaw vs MCP)
Replies: 2
Views: 2728

Re: Reversing directions at limits (Roboclaw vs MCP)

I don't think there is a command to read all of the digital inputs, and the "flip switch" input only works in "RC/Analog" modes. Nor are the limit switch inputs readable via the API. However, you can read the "home" switch input state via the "Read Status" command (90). If you were to connect your p...
by cyberdemon
Sun Oct 08, 2017 3:52 am
Forum: Velocity and Position Control
Topic: Safety stop on loss of Serial Connection
Replies: 13
Views: 9709

Re: Safety stop on loss of Serial Connection

Hello, I was wondering if you had finished considering this yet? I was quite surprised and disappointed to find that the RoboClaw controllers don't have this safety feature. Given that these drives also don't have any gross error limit setting, then all of the closed-loop commands, including 'distan...