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Ignorant beginner looking for a start

DGunthert

May 21, 2014
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May 21, 2014
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I've got an Endless Pool set up on my back deck. For those that don't know, it's basically a treadmill for swimming. You can change the speed of the current using a remote key fob. The receiving board has an RJ-14 jack for output that allows you to hook up a pace display that gives a rough estimate of your pace per 100 meters. The downside is the display is $150. Seems a bit steep to me for what it is. I don't really care about what the alleged pace is. I wouldn't trust that it was accurate anyway. However, since I do increase and decrease the speed of the current quite a bit as I warm up and do intervals of different intensities, I'd like a way to return to the same speeds consistently.

Keep in mind the subject of this post. I really don't have any idea what I'm talking about from here on out.

The circuit diagram for the controller shows the wiring for the RJ-14 jack. Pin 1 is 24 COM, Pin 2 is 4-20 mA OUT. Pin 3 is 4-20 mA COM. Pin 4 is 24 VDC. I measured the voltage across pins 2 and 3. At the lowest speed setting possible, it was 1.238. As I increased the speed, the voltage increased pretty steadily by about .029 volts. All I really want to do is hook up a display that will show that voltage. That would be good enough.

I only need something that shows voltage in the single digits and has 2 decimal places. I'd like something at least a couple of inches high so I can see it relatively easily from the pool. Obviously it has to work off the power output available through the jack. I don't know if I should have a preference for LCD or LED. I have no idea what else I should be saying or asking. Anyone have thoughts, advice, or display options?
 

Harald Kapp

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Nov 17, 2011
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Welcome to our forum.

From the description of the RJ-14 jack I guess the pin's functions are:
Pin4 -> Pin 1 = 24 V DC (Pin 4=positive)
Pin2 -> Pin 3 = current output 4mA to 20mA

A ´current output is meant to deliver a controlled current (not voltage). So you should set your meter to 0-20mA DC current measurement.

From that point on: do you realize that you already have the display you want at hand?
I measured the voltage across pins 2 and 3. At the lowest speed setting possible, it was 1.238. As I increased the speed, the voltage increased pretty steadily by about .029 volts.
This is what you need, isn't it? Buy a (very) cheap multimeter and hook it up permanently to measure the current from Pin 2->3.
There you go.
 

DGunthert

May 21, 2014
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May 21, 2014
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Welcome to our forum.

From the description of the RJ-14 jack I guess the pin's functions are:
Pin4 -> Pin 1 = 24 V DC (Pin 4=positive)
Pin2 -> Pin 3 = current output 4mA to 20mA

A ´current output is meant to deliver a controlled current (not voltage). So you should set your meter to 0-20mA DC current measurement.

From that point on: do you realize that you already have the display you want at hand?
This is what you need, isn't it? Buy a (very) cheap multimeter and hook it up permanently to measure the current from Pin 2->3.
There you go.

You're right, what I was measuring will suit my needs. I'd rather have something that's powered using the 24V supply that's on pins 1 and 4 (I'm assuming that's what the OEM's display uses.. I also want to make it fairly permanent and weather proof. I haven't had much success finding a display that would meet the requirements.

Scratch that, I think I just did. Sanity check please:
http://www.amazon.com/SMAKN-Waterproof-Digital-Voltmeter-0-100V/dp/B00K3GJ5PM/ref=sr_1_15?s=hi&ie=UTF8&qid=1400770320&sr=1-15&keywords=4+wire+DC+voltmeter

Measure range: DC 0-100V; Power Supply: DC 4.5-30V
Permissible Error: 1% (+ / - 1 Digit)
Display: three 0.56 " LED digital tube
Display Color: RED
Refresh rate: about 500mS
Current consumption: about 5-20mA
 

shrtrnd

Jan 15, 2010
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3,876
What you're looking at is the power circuit to the board; and in the U.S. anyway, the separate industry standard 4-20ma signal control loop.
There are oodles of readily available digital displays available that will show you that industry standard (industrial) 4-20ma signal in any format you want:
incuding the 4-20ma, 1-5VDC signal you want to see.
Google Red Lion, Omega, or a dozen other signal loop conditioner manufacturers.
 

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