Created Date: January 05,2007

Created by: AZRoger

Status so far:

Input Module D2-32ND3

takes 24 vdc inputs

On signals need to be over 19 vdc per specification.

Off signals need to be under 7 vdc per spec. (clamping resistor pulls signal to ground in NC case)

Nominal 4800 ohms input impedance

input circuit has series resistor (current limiting?) and clamp-to-ground resistor, values not specified but total is 4800.

Leviton Commercial Occupancy Sensor OSW12-M0W

runs on 24vdc, draws 16 to 20 ma depending on how many LEDs are lit up

open circuit voltage on signal lines (blue/gray) is 22.8 vdc when on

open circuit voltage on signal lines is 0.0 vdc when off (no one there)

when signal line is connected to the input module

on voltage is 14.7 +- 0.1 vdc

on current is 2.9 ma

The AD input module usually recognizes 14.7 vdc as ON but this is way out of spec.

I tried Pull-up resistors of various values and had no luck. Values that would raise the OFF voltage to over 1.4 vdc only raised the ON voltage by 0.1 vdc. Looks like I'm going to need to add an amplifier transistor to get enough signal to drive the input module. As I recall, the 2N2222 is pretty bullet proof up to 30 volts or so.

Anyone have an idea of how to handle this low current, 24 vdc source into regular digital input modules?

Roger

Created Date: January 05,2007

Created by: AZRoger

Elevmike,

Can you suggest a specific part? I searched the web and the 24 vdc reed relays I found had coil resistance of 2000 ohms or so which is about 12 ma. My signal is very weak and will only push 2.9 ma into a 4800 ohm load. And the voltage at that output is already under 15 volts. The logic box that is part of the standard setup for this sensor must have very high inpedance inputs.

If a really low energy reed relay is NOT available:

I'm considering using an LM741 op amp. This has a really high input impedance (over 100K ohms) and can drive 25 ma or more. And they 're cheap. Have you, or anyone else out there, used these when signals are very weak?

Roger

Created Date: January 06,2007

Created by: elevmike

Rodger,

There's something wrong here? I reviewed both the spec sheet and the installiation instructions for this unit and cannot find a current rating on the output. However the output voltage is 24vdc, but that is dependent on the power supply. This would supply a +24vdc source that should be able to signal a sinking PLC input configuration.

The PLC input module and the occupency detector should share the 24vdc power supply. The PLC input common would be connect to the black wire. The red wire would be the +24vdc, the Black would be 0vdc (reference, or 24-). When activated the blue wire should read 24vdc between the blue and black wires (with no other load on the blue wire). To fire the PLC input requires 20vdc @ 3.5 ma. If the blue wire is connected to the PLC input you should see a signal. If not check the voltage on the signal. If the voltage is low, the check the main 24vdc power supply. If the power supply is at 24vdc but the signal is low, then I would suspectd a faulty detector, or a bad connection causing voltage drop between the detector output and the PLC input.

In short I cant believe that the detector output cant pass 3.5-8.0 ma without causing a dramatic voltage drop, but I cant find any details on the output device in Leviton's documentation. You might have to call them.

Consider the possability that you might have a faulty detector and try another one.

Created Date: January 12,2007

Created by: AZRoger

elevmike and jesawyers,

Thanks for your interest and suggestions.

I tested a second OSW12-M0W Occupancy Sensor and got the same results. I think is part of their Class II and short circuit protection to provide very little drive to the signal leads.

I ran a series of tests with different resistances between signal and ground. I put all the numbers in an Excel spread sheet available at

http://www.shotscan.com/AD/OccupancySensor01.xls

To make it work, I used a TL082 OP Amp to boost both the Gray and Blue outputs. The solution is a bit of a hack -- lots of hot melt glue and some wire and solder. With the OP Amp in the circuit I get 23.2 volts and 4.53 milliamps to drive the PLC module input. Sweet.

A graph of the results and a couple pictures of the solution are included in the Spread Sheet. The pictures are small but I think you can select a picture and pull a corner out to make it bigger on your screen. If you have trouble with the spread sheet (and care) let me know and I'll post the JPGs and text separately. The graph would probably be a screen shot.

Roger

Created Date: January 13,2007

Created by: AZRoger

KPrice,

Thanks for the lead. Looks like I'd need to run the field wiring through grommets in the sides or top or bottom of the case and hook it up with the cover off. It would be very tidy with the cover on. The smallest of the enclosures could easily handle a dozen channels of OP Amplification, including the terminal blocks.

Are there other sensors that put out too little juice? Is this a way to clean up noisy signals? Is this Amplifier Box something that might make a product opportunity for AD or some eager entrepreneur?

Roger

Created Date: January 13,2007

Created by: jesawyers

AZRoger...I was looking again at the sensor to see what kind of PCB/enclosure would fit this need. I found that the sensor has an option that includes a form C relay. Quoting from the document...

"Power packs provide power for occupancy sensors as well as load switching circuitry.

A Leviton Power Pack is required with any low voltage occupancy sensor. Add-A-Relay

units can be used to expand control capability. "

Check out page 15 of the document below. I think this is what were trying to do.

John

http://www.smarthomeusa.com/Common/leviton/manuals/Occupancy/OccSensor-ProductGuide.pdf

Created Date: January 13,2007

Created by: AZRoger

John,

You 're right. This is the power pack Leviton spec's to drive the sensors. I didn't find them in my prior searches. With this new information, at about $32 each and having to supply 110VAC for each, and still having to wire the relay to 24VDC to drive the input, I still think a 24VDC only solution is better. There seems to be lots of packaging and extra wiring just to accomodate 110vac for the module and a variety of voltages for the load.

I 've done two sensors by kludging at the sensor. For the next batch, I think I'll try to modify DN-TL14 three level terminal blocks to do the job. The bottom would be GND, the middle layer 24vdc, and the top path could be cut to provide signal in and out. This allows pluggable jumpers to pass power between the blocks with the signal in and out not being plugable. Some of the internal plastic ribs will have to be cut. The top may need some epoxy to hold the teminals in place after they are cut. But there's room in there to fit the OP Amp without making the terminal block any thicker. http://forum1.automationdirect.com/board/smile.gif

I'm very stingy with DIN rail Space. I use ZIP blocks with stacked and staggered connectors to get 32 I/O points in 4 1/2 inches (114 mm). The system I'm working on now has 256 discrete outputs and 384 discrete inuts. I have only 8 inputs to boost so spending 1/4 inch (6 mm) per input is OK - and probably worth the space to keep the sensors "stock ". I can afford a couple inches. If all my inputs needed to be boosted, I'd need 8 feet of DIN rail just for terminal blocks using just 1/4 inch each...........

Anyway, thanks again for the pointer to the official Leviton solution. And let me know if you try a PCB in a BOX solution.

Roger

Created Date: January 12,2007

Created by: jesawyers

AZRoger...Thanks dude for all your work! I 've ordered one of the sensors and was going to install it in the next week or two.

Question...Can you sketch the TL082 circuit and post. I'm wondering if we can make a small PCB with terminal blocks on a DIN rail mount near the PLC. This way we can run the sensor wires to the amp without modifying the device and voiding any class rating.

I 've done some PCB prototyping in the past and I'm thinking an external amplifier would be a cleaner solution. If the sensor fails and needs to be replaced you have to make the mod again.

Later...John