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HVAC Monitor Instructions?

cadillackid

New Member
I just purchased the HVAC monitor and case.. I found on the website the pinout for a "typical" RJ45 connector but am definately not sure what all needs to be present to make this thing work and I dont want to destroy it.

where do my inputs from the HVAC go? im assuming on the terminal strip on Q1,Q2,Q3,Q4? which terminal is common?

will this work on a parasitic power 1 wire Net or is it required that I provide Power to the device?

if there is a web page pointing to a document on this little guy it would be great.. I didnt find this device in the "how to" on hobby board's website.

-Christopher
 

ericvic

Active Member
Christopher,

I thought I had already added an HVAC doc to the website but I guess I missed that one.

Anyway there should be some text on the board right above the screw terminals. You need to attach common to the GND terminal and then the other inputs are wired in parallel with the termostat and go to the A,B,C and/or D inputs.

You can run the HVAC Monitor parasitically by removing the jumper on the board.

Eric
 
Christopher,

I thought I had already added an HVAC doc to the website but I guess I missed that one.

Anyway there should be some text on the board right above the screw terminals. You need to attach common to the GND terminal and then the other inputs are wired in parallel with the termostat and go to the A,B,C and/or D inputs.

You can run the HVAC Monitor parasitically by removing the jumper on the board.

Eric

I must be the "other" guy using this board. :( I'm also finding no docs for it on the website. I'm running the "black" and "red" lines from a PC power supply to the "A" and "GND" terminals on the device, and I'm putting power on the device through a 6-port hub. 11.55V on the terminals shows as .99V. Must be scaling going on.

Could I be missing something? (Er..something new?)
 

ericvic

Active Member
I must be the "other" guy using this board. :( I'm also finding no docs for it on the website. I'm running the "black" and "red" lines from a PC power supply to the "A" and "GND" terminals on the device, and I'm putting power on the device through a 6-port hub. 11.55V on the terminals shows as .99V. Must be scaling going on.

Could I be missing something? (Er..something new?)

The HVAC board was originally designed to basically just give an indication of when the AC unit was on or off not to measure the actual voltage. The voltage that will be measured can be figured roughly based on this formula 1/10(input voltage - 1). The minus 1 is because the BAS16 diode on the input (used to rectify AC input voltages) has a forward drop of 1v. Then there is a roughly 1:10 voltage divider to get the 28v used in HVAC units down to a level acceptable to the DS2450.

Eric
 
The HVAC board was originally designed to basically just give an indication of when the AC unit was on or off not to measure the actual voltage. The voltage that will be measured can be figured roughly based on this formula 1/10(input voltage - 1). The minus 1 is because the BAS16 diode on the input (used to rectify AC input voltages) has a forward drop of 1v. Then there is a roughly 1:10 voltage divider to get the 28v used in HVAC units down to a level acceptable to the DS2450.

Eric

Ahl ok. I ferreted-out a coeffecient that got me within .1V; I'll try your new numbers when I get the sensor-net re-assembled. I got the equipment-room cooling loop, and the power-management loop worked out, with a glorious display on the LCD, but now it's time to start installing the stuff so it can start turning on fans, lights, etc. I'll have pictures eventually; this is a lot of fun!
 
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