PG 500 & 1815 Radar

[NickTF]

Hello, I purchased a PG 500 used from Max Marine at the suggestion of a local electronics supplier stating that furuno products have outstanding reliability. The heading sensor was purchased to supply the 1815 radar I intend to purchase with the heading information needed for true trails, ARPA, etc. The GPS will be sent out of my Humminbird Helix 10 (sorry guys, the mega side imaging is hard to beat in these units).

My initial question is in regards to positioning the pg 500 as it relates to the 1815 display unit. Ideally, i'd like to have the two close together on the dash of my Defiance Pilot House 250. My question/concern is, will there be interference if I mount the PG 500 within 6" or so of the 1815 screen? I'm leaning yes given the 1815 will have a cable for power and input from the radar but figured i'd ask the experts here.

Thanks. I'm thinking this will be the first of many questions as I'm a DIYer with only 6 or so hours of researching how nmea 0183 works and how to get it out/in my Humminbird.

 

[NickTF]

Also, might as well ask. I was able to dig up the color coding of the pg500 before I have it in hand as it pertains to the power/data cable. Looks like it is as follows:
black (power Neg)
red (+ DC)
blue (- NMEA out)
green (-NMEA in)
white (+ NMEA out)
yellow (+ NMEA in)

I'm connecting the PG 500 to my Humminbird Helix 10 g2n MFD via the AS HHGPS NMEA cable (goes to com port of Helix). It's color codes are as follows:
Red (+DC)
Black ( ground)
Green (NMEA Receive +)
White (NMEA Transmit +).

The NMEA connection appears simple for getting heading into the Helix, white from PG500 to green from Helix. My question is regarding ground and power. Would I not just connect the black from the PG500 to the black from the Helix? Would I not just connect the red from the PG500 to the red from the Helix? How can I be sure the Helix supplies the appropriate amperage for the PG500 (is there a spec I can check)? Is the ground of the Helix sufficient to ground the PG500?

I'd presume the AD10 port should be used to get the heading signal to the 1815 when I add it later?

 

[NickTF]

http://www.shipmodul.com/en/connections.html

I have a feeling i've confused power/ground I inquired about in post #2 with getting actual power to turn the PG500 on and off. I believe the red/black wires asked about in post #2 are just for signal conveyance and don't power the equipment at all. Is that correct? The link above explains it I think.

Sorry, i'm 100% green on NMEA 0183.

 

[Taniwani]

Seems that the Hummingbird unit uses RS232, whereas most NMEA0183 connections are RS422. You will need an RS232 to RS422 Adapter in between.

 

[NickTF]

Seems that the Hummingbird unit uses RS232, whereas most NMEA0183 connections are RS422. You will need an RS232 to RS422 Adapter in between.

Can't I just make a single ended connection from the pg500 to the helix? The cable run is very short.

Now here is a brain teaser, since I need the Helix to receive data from the pg500 and output data to the 1815, can the ground wire of the Helix be shared by the PG500 and the 1815?

 

[Taniwani]

It's likely that connecting the DC grounds and Rx+ together and using Rx- and Tx- towards the single ended RX and TX will work.

But you should be aware that it is more by accident than design, as the voltage levels are also different. And it is a really bad practise to tie DC grounds together, thus creating ground loops. Inevitably, part of the supply current of the devices will then go over these connections and introduce noise.

That's why I recommended using a galvanically isolated adapter that uses opto-couplers.

 

[NickTF]

It's likely that connecting the DC grounds and Rx+ together and using Rx- and Tx- towards the single ended RX and TX will work.

But you should be aware that it is more by accident than design, as the voltage levels are also different. And it is a really bad practise to tie DC grounds together, thus creating ground loops. Inevitably, part of the supply current of the devices will then go over these connections and introduce noise.

That's why I recommended using a galvanically isolated adapter that uses opto-couplers.

Thanks. I suppose it is something I can try and find out if it works and is stable. If it doesn't then I can invest in the adapter with the noted features.

I figured out last night that the pg500 also has a ground in the nmea/power cable that i'll be hooking up to the Helix. From what I understand a single ended connection from an rs422 to rs232 unit should be as follows: transmit positive from pg500 to receive positive from Helix, ground from pg500 to ground from Helix. When I get the 1815, the connection will be as follows: transmit positive from the Helix to receive positive on the 1815, ground from the Helix to ground on the 1815 (as noted the Helix ground will be shared with the 1815 and the PG500). Or, will the ground from the Helix go to the receive negatived of the 1815? Sounds like the worst case is it just won't work or work reliability then I can take other measures. I'm all ears if there are additional concerns with this plan outside of what's been pointed out above Taniwani.

 

[Taniwani]

I think that both, PG-500 and the 1815 Radar have optically isolated NMEA ports. That means that the signals on Tx+/- are totally unrelated to DC ground and that connecting Tx+ of the PG-500 to RX on the single ended device would achieve nothing, wether you connect the two DC grounds or not.

So instead of connecting the DC grounds, take the DC ground of the single ended device and run it to Tx- of the PG-500. (Of course also connect Tx+ to RX). That should get your heading in the Hummingbird display.

The caveat here is, that I'm not entirely sure about the optical isolation of the differential output of the PG-500, if it is not, you could damage the driver on Tx-. To be on the safe side, you could put a 120Ω resistor in series on that line. I don't have a PG-500 and I don't have a 1815 radar, so I cannot tell you for sure, but all the Furuno devices I have, have isolated ports.

For the GPS data to the 1815, take TX of the single-ended output and connect it to Rx+ of a free NMEA port on the 1815. And run the DC-ground of the Hummingbird to Rx- of the same port on the 1815. That direction is not potentially dangerous.

As in that case (of assumed optical isolation of the RS-422 ports) DC-ground to DC-ground connections are not needed and just add to the problems. I strictly avoid ground loops on my boat as I have seen so many problems on other boats, and these byte you when you don't expect it, just because something changed in another corner or some connection goes bad.

Good luck.

 

[NickTF]

Thanks this is great information!!! I will call Furuno and see if I can find out about the isolation of the PG-500.

 

[NickTF]

So I just got off the phone with Furuno. None of the ports of the furuno equipment are opto-isolated (equipment in this thread). Therefore, I was told that I'll need to have an opto isolator for each connection (232 to 422 converter) just as you had stated originally Taniwani. Actisense and Noland (something with an Noxxxxx) were suggested. Any links to units which may work are appreciated should someone have this info handy. I've googled these before and most have a serial port connector which won't be helpful considering I need bare wire connections. Thanks.

 

[NickTF]

https://www.serialcomm.com/serial_rs232 ... _info.aspx

I think the above will work, I'd just have to purchase the rs232 terminal block adapter than make my connections.

 

[Taniwani]

Have you noticed that this unit would need a 9V power supply unless you want to run it off an AC inverter.

As you said, most of these adapters have a DB9 plug on the RS232 side and that is because NMEA over RS232 is hardly ever used between marine devices, but only to interface with PCs or some handheld GPS units. Usually these adapters draw power from the interface lines of the PC and these may not work with units that just supply RX and TX and GND.

Your Hummingbird unit seems to have a red power wire on the interface, the question is, what voltage it would send out. If it is just a pass through of the ships 12V power, this may be too high, especially during charging for the unit to pointed out.

As an alternative you may want to look at the Actisense OPTO-4. Like most it has a DB9 female plug on the RS232 side, and plain wires on the RS422 side. You could obtain a male DB9 plug and wire your RS232 to it: RX on PIN2, TX on PIN3, GND on PIN 5 and anything between 9V and 12V to PIN7 to power it.