Any electronics guys on the board?

[Ugla]

I just set up an Aqua Controller and am having problems with wrong PH readings when I connect it to my computer with a 50' serial cable. Neptune Sys recommends a $50+ Ground Isolating Serial Connector. Its a small box with male and female DB9 connectors on it. It basically eliminates ground loops between the controller and computer

Can anyone draw a diagram so i can build my own?

Jim

 

[pat99016]

Just disconnect the ground from one side of the cable - usually the probe side.
Pat

 

[Ugla]

no worky

That did not work. Now it will not connect. There are only 4 wires used in the cable:
External Switch Input
Serial Transmit Data
Serial Receive Data
Ground
Any other ideas?

Thanks!

 

[DonW]

You get a grounding loop problem because your using two different power supplies one at each end. The opto isolator will cost you more than $50 to build after you ship in all the parts. One way around this is to power the controller using the pc's 12vdc supply and using resistors to make the voltage appropriate. Which basicly means running a 50ft power wire to the controller. I think I'd just spend the $50.
If you want to go the other route you can open the db9 cable and use one of the unused conductors for dc+ and another for dc- to power the controller. Snip the conductors so they no longer go to the pc and take 12dc from your pc's power supply.

Don

 

[mower7]

I would agree with Don. By the time you spend the money on the hardware you would need. Spend the time making the thing. Then the time debugging the thing. Then the time dealing with strange behavior every once and a while. It will end up costing you more than $50 in money/blood/sweat/tears... Plus having a nice finished product that doesn't look ugly and can stand the reasonably harsh environment of the aquarium stand is nice too.

Jack (just my 0.02)

 

[Ugla]

Ok, I am convinced I will buy it. Thanks,

I was hoping it was something cheap to do.