Power supply for the reach RS2

I’ve seen partial answers to these question in the forum, but i haven’t found a complete answer.

I have an RS2 and I want to set up a permanent power supply for it. I believe that this can be done via the RS/232 serial port.

At present, I just want to power the RS2, I don’t want to receive data over that connection.

I have the Emlid serial cable that connects to the serial port and has a DB9 connector on the other end. I now need something that terminates on DB9 and produces power of the right form on the right pins. This will allow me to create a nice tidy power supply without any bodges.

Question 1: is there a ready-made solution out there that will do that job - for example, an RS/232 board for a PC that supplies suitable power over the serial connection?

(I suspect that the answer is no, but it’s worth asking.)

If not, I need to make up a suitable power supply terminated with a DB9 connector.

I believe that a 5V supply will do the job.

I see that to power the RS2 I need to supply between 7.5W and 10W.

So I think that a power supply that produces 5V and 2A will do the job.

Question 2: is that correct? Will that setup run my RS2? (Not just charge it, run it.)

If so, I plan to buy a suitable power supply, cut off the termination and wire the output to a DB9 connector.

I found a pinout diagram for the serial port here: https://docs.emlid.com/reachrs/assets/files/RS232-port-74a06cef27a21512f4562c14e3727679.pdf

This is for the RS, not the RS2. It says that pins 1, 2 and 3 are ground and pin 9 is 5-20V input.

Question 3: are the pinouts the same for the RS2?

If all the above stacks up, I believe that I will need to connect the red wire from the power supply to pin 9 of a DB9 connector and the black wire to pin 1.

Question 4: is that correct?

Finally, having bought the Emlid serial cable, I plugged it into the RS/232 socket. The locking pins sprung out and now I can’t see how to disconnect the cable.

Question 5: once the cable is plugged in, is it possible to remove it and, if so, how?

Hi @simonritchie.uk,

To power Reach from a bottom connector, you need a cable without a second connector.

DB9 is a data-transport connector, so cables with DB9 don’t provide power input. Here’s a pinout for this cable.

Also, here’s a pinout of RS232 port on Reach RS2. As you can see, it supports 6-40V input. So 5V isn’t enough to power Reach RS2.

There are indeed no ready solutions. But you can search this forum for some examples. Here’s one of them, where guys used 12V 15A transformer. From the Reach side, you need 6-40V input and one of the GND pins.

once the cable is plugged in, is it possible to remove it and, if so, how?

Usually, you just need to pull the ring attached to a cable near RS232 connector. Does it work?

Ah, so I can use the serial port to provide power OR to receive data, BUT NOT BOTH. That’s not very clear from the documentation.

Actually, this whole issue could be much better documented.

There’s a response from Emlid in this thread: RS2 external power - #4 by noel

The response says: " To charge the receiver 5 watts is required. For operating 7,5 watts on average is required (10 watts maximum)."

12V at 15A is 180 Watts. Is it safe to provide 180 Watts? If so, what does “10W maximum mean?”

Obviously I don’t want to spend more on electricity than i need to, so I need to understand the ideal working supply specification.

DB9 is a data-transport connector

Is it wired as standard RS/232? If I run the RS2 from a battery and connect the DB9 cable to a serial port on a PC, will the PC be able to pick up the data? That would be useful to know.

Usually, you just need to pull the ring attached to a cable

that worked. Thank you. I was wondering what that ring is for! Again, it’s not awfully clear.

Thanks for the information so far.



Hi Simon,

You can do both, but not via RS232-DB9 cable. Exactly this cable doesn’t support power input.

That’s correct. 10W maximum means that Reach won’t take more than 10W, but if power supply provides more, it’s not an issue. I agree the phrasing in docs isn’t fully clear here. We’ll think about it.

PC will be able to pick the data, but you can’t power Reach from DB9.

Many thanks. That’s much clearer.

So, a 6v 1.5A power supply will give me 9W and that should do the job.

I’ll order the parts and if it works I will annotate this thread with the details.

It would be great! You may even be interested in sharing your project details in the Project Share category here on the forum.

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