Components for Converting AC->DC + voltage step-down + reversing of polarity

[whytwo]

Hi all,

First, I really appreciate anyone taking time to read through this and provide feedback.

I’m working on a unique HVAC application where I have handful of problem statements and I’m trying to figure out what the most ideal components are. Additionally, I’d like to be as minimal as possible! For example, if there were a single device/PLC/relay that could do it all (even if pricey), that’s OK.

My preference would be to take off-the-shelf component(s), if possible.

Here is what I’m working with:

-My HVAC Zone Controller outputs 24vac designed to Open/Close Dampers (a typical HVAC actuator is 24vac).

-My Damper Actuator motors are 9vdc (mine are NOT typical).

-My HVAC Zone Controller has three 24vac outputs to Open/Close Dampers: 1) Common 2) Open, and 3) Close. (so common is always used, but the Open/Close terminals are used for their respective actions)

-My Damper Actuators have two wire inputs to Open/Close these Dampers. Since this is a DC motor Actuator, you simply reverse the polarity to Open/Close the Dampers.

So, when my HVAC Controller wants to Open a damper, it outputs 24vac to Common/Open terminals, and when it wants to Close a damper, it outputs 24vac to Common/Closed terminals.

I have a multimeter watching those outputs and it’s working as expected.

I am looking to Convert from AC -> DC, as well as step-down from 24v to 9v, as well as reverse the polarity of 3 wires to 2.

I believe I’ve identified components that could do everything… i.e. a Voltage Rectifier (to go from AC->DC), a transformer to go from 24vdc->9vdc, and then a Dual Pole Dual Throw Relay (DPDT) to reverse polarity of the DC motor…

Question is: Can any recommend the “cleanest” way to do this?

Another note, I have about 8 DC actuator Damper Motos per floor (3 floors total), so if there were some sort of DIN-mounted PLC/Relay/Rectifier module(s) that could take a number of inputs and outputs, that would be brilliant!

Some additional details:
-DC Damper Actuator motors draw 250mA.
-Zone Controller's AC Output is 2.5Amp max
-There is a use-case where multiple DC Damper Actuator motors may be connected to a single Zone Controller Output. (i.e. Zone Controller Open/Closed circuits could control up-to 3 Dampers)

Please let me know if you have any questions and thank you again!!

 

[whytwo]

Just giving a quick update -- I got a new round of PTC Resettable Fuses today, including a "Fast Blow" @ 100mA (Ceramic) from Bourne.

This Resettable Fuse is actually working VERY WELL... seems to stop it just like the tool does whereas the Bel that was working the best prior didn't below for 2+ seconds and I could hear the motor grinding longer than I wanted... (it also got 215F+ whereas the Bel seems to max around 174F, so notably less...)

I also recorded a short video to show the current situation with actual Damper+Duct products (prior I was just testing with spare motors, now I have the whole thing). What I'm testing with now I already have installed throughout my walls...

New video by true

photos.app.goo.gl

I should be getting my current monitoring and timer relays tomorrow so I can play around with those before determining which of the two solutions is optimal, but this seems to be working very well compared to where I was a few days ago... ha. Question is: can it stand the test of time and be reliable without breaking behind-drywall damper actuator motors....? I think I can set Thermostat Schedules to open and close dampers every 10 minutes and if that works for maybe a month with no issues, I'd be fairly confident!

Thanks again for everybody's help.