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POST No. 2407347
DXL Pro overheating problem on power cables
2019-03-15 09:34:38 imarvi2

Hi,


I have found problems of overheating with the power cables of the DXL H54Pro (those supplied with the actuator). I have power the Dynamixel with a 8000mAh, 25C battery.


Could you confirm which is the max current they bear in continious operation? and the peak one for a momento?


Thanks,


Iván M.

2019-03-15 09:34:38
imarvi2
2019-03-18 04:48:44 ivan martinez

Hi,

In the mean time I have gone deeper into the issue, and I'm actully very confused:

- Following the manufacturer (Molex) the current limit for the Crimp Terminals and the PCB Header supplied with the DXL 54P  (MOLEX 39-00-0038 and MOLEX 39-28-1023) is just 9 Amps.

- On the contrary the e-manual states that on a continuous operation the DXL 54P-200 works at 9,3 Amps with a torque of 44,7 Nm


So, that means that it is not possible to go beyond those 44,7 Nm - 9,3 Amps?


I would like you to clarify the issue as for the application I am working in, I need to reach peaks above 9 amps (12-13!)...


I look forward to your reply.


Regards,


Iván M.




2019-03-18 04:48:44
imarvi2
2019-03-18 13:39:11 Will Son

Hi,


The connector information written in the manual is describing compatible products and the components may not identical to the one that is used in the product.


It is recommended to use DYNAMIXEL PRO series within a continuous operating range.

Intermittent use of higher current exceeding the continuous operating range can be acceptable, but it should be carefully performed as it can cause temperature rise and power brownout for other connected components.


Also when using high current, it is strongly recommended to use a proper power cable along with 4pin RS-485 power supply pins.


Regarding the battery, it is recommended to use 6S Lithium battery which can reach up to 25.2V when fully charged.

7S is too high voltage without enough protection margin whereas 5S is too low voltage which will require more current draw.


Thank you.

2019-03-18 13:39:11
willson
2019-03-18 15:11:57 ivan martinez

Thanks for your answer.

 

I confirm that , apparently the components on my dynamixel 54p are those shown on the e-manual as I described before.

 

I have two questions:

 

- Do you mean that I have to use the Rs485 port (that intended for communication) to power the dynamixel for high current? I understood in the e-manual that that was only intended up to 12V, and that for Dynamixel54 (24V) independent power source had to be used?

- It's not a problem to increase the cable section (+20awg) and the housing crimp terminal according to Molex specifications so that it could bear 13 amps. But If the Pcb Header is molex 39-28-1023 it would not work. Is that correct? Do you advice any solution?

 

I look forward to your reply.

 

Ivan M

2019-03-18 15:11:57
imarvi2
2019-03-18 19:36:10 Will Son

Hi,


What I meant is that you can use RS485 port power pins along with the power connector at the same time.

The power pins of RS-485 connector and the main Power connector shares the identical VDD and GND.

In this way, you don't have to worry about exceeding the current rated for the main power connector.

Thank you.

2019-03-18 19:36:10
willson
2019-03-19 19:40:39 ivan martinez

Thanks Willson.


So, I still will need help to understand how I should arrange it. Could you advice me?


My application works with 2 Dynamixels 54P and 1 OpenCR.


So following what you adviced me, I imagine that I have to connect one of the RS485 ports of each DXL directly to the 24V power source. Then as I would only have 1 RS485 port left for signal, I would have to connect it directly to the OpenCR (not daisy chan anymore)? I attach a file with the sketch I have in mind.


Could you confirm if Its that the correct way to do it? If not could you let me know how to do it?


Looking forward to your reply,


Iván M.
2019-03-19 19:40:39
imarvi2
2019-03-20 12:00:56 Will Son

Hi,


If you want to keep it as a single connection to OpenCR1.0, you can connect as below.

Please note that you should not supply VDD from DYNAMIXEL toward OpenCR1.0 if you are not using the identical power source for DYNAMIXEL and OpenCR1.0.

Also, in case of high power usage, it is recommended to separate power sources for the controller and actuators to minimize interference.



Other option will be using separate cables for each DYNAMIXEL to connect to OpenCR1.0.

You'll still be able to use your system without any changes in your code as OpenCR1.0 RS-485 ports are already connected internally.

However, in this case, you should also remove the VDD pin between OpenCR1.0 and DYNAMIXEL PRO+ to protect reverse voltage and interference.


Thank you.

2019-03-20 12:00:56
willson
2019-03-20 14:35:47 ivan martinez

Great Willson! I'll arrange it as proposed.


Thanks a lot. It was really a very usefull feedback :)


Iván M.

2019-03-20 14:35:47
imarvi2
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