Relay boards supports WebControl TTL output

[CAI_Support]

We have a few customers told us that most of the low cost relay boards are TTL low active. That will not work well, if you have critical control that not tolerate power loss caused relay malfunction, please select TTL high active relay board. 
 
We noticed on eBay, there is sellers selling those.  For example, this item:
http://www.ebay.com/itm/130806508025
 
is one of those 12V coil relay board.

 

[CAI_Support]

If you want to use it for HVAC control, this 24V coil relay board will work
 
http://www.ebay.com/itm/400343390234

 

[az1324]

HVAC uses 24VAC typically and even so shouldn't steal power from the hvac supply to power your relays unless you know it is available.

 

[CAI_Support]

az1324,  if you look inside thermostat, they all have relay inside that powered from HVAC power supply.  Normally configuration is backed up by two AA batteries.  It is easy to have a bridge rectifier to make 24VAC to DC and power that relay board.  Because of 24V, it takes very little current.

 

[CAI_Support]

The 24V Omron relay model number G5LA-14-DC24 coil current is 15mA at 24V, coil resistance is 1.6K.  The smallest HVAC 24V transformer output current is 2.08A at 24VAC.
 
Great care must be taken not wiring wrong.  For two stage AC and furnace, there are up to two white wires and two yellow wires.  White is for heat, Yellow is for cooling, Green is for fan. However, some companies not follow the color coding on them.  You will need to verify the terminal label for sure.

 

[az1324]

Most modern thermostats use triacs. Rectification may require smoothing capacitors. But there are different design choices for every problem.

 

[CAI_Support]

AZ1324,  That is true. Some HVAC units are using PWM control the motor speed these days -- so called variable speed system.  They are significant more expensive than two stage systems.  Last I checked the Maytag and Lennox, both still use 24VAC transformer for powering the control system.

 

[Machineman]

I found a relay board on amazon.com that activates on a high state. For some reason I can paste links here but its called "Generic 16 channel......."  Its $36 and comes in Relay 5V or 12V.  The 5V individual relays are spec'd up to 6.5V max so you can run 6V to power the relay board and WC32 with the same supply. So far no issues.

 

[CAI_Support]

Great to hear.  Some of us having problem paste anything to this site.  We have to manually type in the URL, if we want to post it.  I think the problem is in both browser security and site security conflict.

 

[LarrylLix]

Great to hear. Some of us having problem paste anything to this site. We have to manually type in the URL, if we want to post it. I think the problem is in both browser security and site security conflict.

I use the "code" insert function. Look above the input box for the "<>" symbol.
After closing the code input box you can drag and drop it anywhere into your text.
 
Other than that I cannot paste anything into the forum. Quote never worked despite turning of any possible offenders

 

[CAI_Support]

http://www.amazon.com/Generic-Channel-Module-Expansion-Arduino/dp/B00GGKHVBY/

Like this way?  That is great to help post URL for that relay, just this site is not able to get the proper credit for referral without adding the referral link.

 

[Machineman]

Yep, thats the relay board. I tested the 5V version.

http://www.amazon.com/Generic-Channel-Module-Expansion-Arduino/dp/B00GGKHVBY/