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Updated Picture and Schematic
03/10/2022 at 21:59 • 0 comments -
We are in business.
12/06/2021 at 02:36 • 0 commentsFinally working PCB!
At the moment it is working as expected with no issues but with a reduction in functionality vs what was originally intended. The temperature monitoring is not implemented or hooked up. Also the SSR used to trigger the furnace fan is not being used. Fundamentally, the problem is solved but I'd like to take it a step further.
Optos were replaced with a K844P quad opto. With the extra board space I reduced the complexity of the installation by having this device simply sit between the thermostat and the furnace. Adjacent to each connected screw terminal on the left side in the picture is a terminal connected via a direct trace. This prevents having to jam multiple wires into a single screw terminal. Just makes it clean and easy.
Based on the arduino serial print, the boost fan speed is being ready correctly. I've got the board running on a sparkx arduino clone but will move to a FreeTronics EtherTen shortly once I have a place to monitor the data. -
BreadBoarding to Victory
09/04/2021 at 03:34 • 0 commentsI intend to do a new PCB shortly that encapsulates everything. If that works on a traditional arduino, I'm going to try it on the EtherTen from Freetronics and try to get the ethernet communication side of the code up and running again.
Major changes I made:
1. Consolidated my 4 optos into one component. Made board layout much tighter and compact.
2. I learned that since the fans onboard control circuit has its own isolation, there's little risk of issues or noise so there was no worry about hooking ground to ground between my fan controls and the 'duino. I feel the etherten might have been a little more sensitive but we will soon see.
3. Figured out that a little pull up help on the Tachometer circuit does wonders for a clean and reliable reading. I was using INPUT_PULLUP but it seems it's just a tad weak.4. Instead of jamming my thermostat wires into a terminal block and Tee'ing off of them in an attempt to share conductors, I decided that I'm going to have my board pass the thermostat signals across it. At the moment I've doubled the moment of screw terminals and bonded the adjacent terminal to minimize the amount the ac signals traverse the PCB.
Does it work? Yeah it appears to.
Did i learn stuff? Sort of. The open collector circuit on the fan i still don't 100% grasp the purpose of all the components on the fan side but i don't think that matters. -
Prospective Opto Replacements
03/16/2021 at 02:15 • 0 commentsI'm using the H11AA1 for everything because... I got it to work... and then yeah i just used it in every position in every iteration. I told myself this was good because "it reduces part count". I'm ordering 10, not 10 million but I was just lazy. Time to for baby bird to leave the nest and find some new components.
My home base:
24 VAC signals from thermostat:
https://www.vishay.com/docs/83608/h11aa1.pdfThis looks like a suitable analog... but requires an order of 1000 from digikey. Just not ready for that level of commitment.
https://www.vishay.com/docs/83726/tcet2600.pdfThis has similar properties and I don't know the ins and outs
https://www.vishay.com/docs/83523/k814p.pdf
Fan tachometer and 10V PWM:Thinking about this one:
https://www.vishay.com/docs/81135/K827PH.pdf -
Current Status and Issues
03/14/2021 at 15:44 • 0 commentsI've attached a link to my current schematic here which I've also uploaded to the project.
Additionally here is the interface schematic for the fan.