Magni Connector Pinouts

General Questions
1

Hi,

We haven’t received our Magni’s yet but I’d like to get started on designing our robot, our design includes some custom electronics and I was curious about the power outputs: the specification says 7A 5V and 7A 12V. Is this provided by the Molex 8981 connectors on the main board? If so what’s the pinout?

Thanks

Richard

1 Like
2

Hi Richard,

They are Molex 8981 with the standard PC pinout.

3

Thanks for the reply Rohan. I was wondering is there any documentation/pinouts of all the connectors on the main board? At the moment all we have to work with is the pictures on-line and I’d really prefer to have some more detailed documentation, it would really help reduce the risk of connecting something to the wrong port and frying the main board!

Thanks

Richard

5

OK that’s fine, would you happen to have a picture of the mainboard showing all the connectors? I’d like to make sure we have all the connectors (Molex, dupont etc) ordered.

Thanks

Richard

6

I noticed you guys posted the Master Control Board Pinout, thanks this helps a lot!! :smiley:

One quick question which of the UARTS do I use to control the motors? Is it P507 or P508 or both? I ask because we will be using an Nvidia TX2 instead of the Raspberry Pi.

With regards to P601 EN Motor and EN Power what is the functionality of these pins? i.e.drive HIGH to enable power or pull to ground to disable? Are main power and motor power switched via MOSFETS?

I ask for two reasons, first we are making our own shell for the robot so we probably will need to add other external buttons for Power etc. Also we have a few other actuators and sensors that need to be connected to 24v so I was wondering were it would be best to plug them in on the MCB.

Thanks :smiley:

7

Where to plug your third party computer in to control the motors

Well we recommend using P508. For you I’d recommend connecting directly to the TX2 serial port. However this port is designed to match a FTDI USB to serial device - so you can plug one of those in directly and connect to USB.

8

How to attach alternative power on methods

The power switches and charging on the robot are on a small accessory board that can be detached. With a ribbon cable with two standard 0.1" connectors you can move this accessory board and place it anywhere on the robot. The accessory board has 2 M3 screws mount points on the front of it. This was done in anticipation of people such as yourself who may prefer to build their own robot shell. Once you receive your robot we’d be very interested to hear your feedback on this particular board to determine if it meets your needs so that we can improve it for future versions. Please reach out via contact@ubiquityrobotics.com once you’ve had a chance to use it.

If you wish to do your own power on switches, yes enable is “high”. The enable signal goes to an ECB that enables switching and power conditioning the ECB drives. For design convenience we drive these through a small resistor with the 24 volt signal that is already present on the accessory board. However they can be driven with a very wide range of signal voltages.

9

Connecting to External Power

We recommend using P1001 if you wish to connect systems that require external 24V. P702 is another possibility although this is not recommended for most users. These connection points do not run through the onboard ECB. This was done for a couple of good reasons:

  1. Running through the ECB would limit the power we could supply through these systems. As it stands P1001 connector can support a current of 27A.
  2. If there was a design error in whatever you connect to a post ECB 24V connector it could destroy the robot. This is more difficult to do with the current design - the likely outcome of a poorly designed circuit is a burned fuse rather than a dead robot.

On both P1001 and P702 there are signals available that you can hook your own power on mechanisms to. P1001 hooks directly in to the Motor enable signal and P702 connects to the 5V Main (which only comes on when you switch on the “main” power). Power enablement is a very broad area, with everything from user operated mechanical switches to simple relays connected to the “enable” signal to sophisticated ECB being possibilities. If you need further advice in this area email contact@ubiquityrobotics.com and we can arrange a brief call.

10

Thanks for the replies David, the information is very helpful. One last question what is the maximum current draw of the Magni Motors + Mainboard so I can spec the connectors and cables appropriately.

Thanks

11

We rate the PCB fuses for 35A. Although typical is more like 1-2A. To be a little more precise the total system draw is 30.75 A when all systems are at rated maximum which is extremely rare.

Couple of fine print type notes: This number excludes additional loads that you might plug in to the 24 volt directly through P1001 or P702. P1001 bypasses fuses and you need to add a safety device on your own board. P702 has its own fuse on account of being in a connector with other accessories that are already behind a safety device.

12

Another question regarding the addition of an emergency stop button, is it possible to isolate the power supply for the motors and pass that through an estop? Or is the only way to disable motor power through the EN Motor pin that controls the ECB?

13

Yes there is an E-stop button on the robot as standard. It is located on a small accessory board that plugs in to P601 along with the power switch and a charging port. You can detach this board and, with a small ribbon cable with suitable connectors place it anywhere you like on your robot, or just leave it where it is - conveniently located on the front of the robot. Now the way the E-stop works is through the EN motor pin which controls an ECB. The ECB and its associated switch completely de-energizes the motor drive circuits.

14

OK that’s great, just one question with regards to the ECB, has it been safety rated?

15

When you get your robot it will come with a list of all the safety standards that the robot complies with. It is a lengthy list - about 7 pages long. So the short answer is that the robot (including the ECB) has many many different kinds of safety rating. We actually spent more on safety certification and engineering than we did on prototyping costs. Quite apart from the issues with a physical E-Stop (relatively high contact resistance vs. a solid state device etc.) a typical physical E-Stop switch would most likely fall short of these standards as most of them are rated for 13 maybe 15 amps while our motors can potentially draw 20+ Amps. The ECB itself is an important part of the safety systems on the robot as it provides current inrush protection, over current protection, over and undervoltage lock out and reverse polarity protection.

A simple in line E-Stop switch doesn’t provide any of this.