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a more simple request (was solar / relay / timer control thread)

henry barbera

Oct 2, 2014
20
after seriously thinking about my original request and the replies i received i'm almost positive i can end up with 80 to 90% of my goal with many less issues. let me start fresh and just trash the original plan.

this is what i want:

if amps at 120 volt > (selected amount, 0 to 15) then break the circuit, after 15 minutes complete the circuit, wait 10 seconds and repeat.

i would like to have ten of these gizmo's built - can anyone help me or tell me who can.

henry

chopnhack

Apr 28, 2014
1,575
after seriously thinking about my original request and the replies i received i'm almost positive i can end up with 80 to 90% of my goal with many less issues. let me start fresh and just trash the original plan.

this is what i want:

if amps at 120 volt > (selected amount, 0 to 15) then break the circuit, after 15 minutes complete the circuit, wait 10 seconds and repeat.

i would like to have ten of these gizmo's built - can anyone help me or tell me who can.

henry

Hi Henry, I am working with Kris on something that maybe able to be repurposed for your needs. I am at the stage of re-checking the board layout before sending it off for production. The device that Kris has helped me extensively with (Thanks!!) is used to sense when there is current flowing in a circuit, when sensed it turns on another device. In your case I think we can program the mcu to your predetermined shutoff level and have the signal sent to another relay to break your circuit and setup a subroutine to reconnect the circuit after 15 minutes, etc. We need to think about a safety relay as well that separates the grid from this device if it senses no input from the grid. For instance, the current circuit I have works off of mains, so if we use a relay that is N.O., while power is on keeping the relay contacts closed, when grid power fails, the relay will go open, isolating the grid from the circuit. Safety for the repair crews to prevent backfeeding and shock. I haven't had a chance to look over the entire previous posts you made, but did see some of it earlier in the week. The circuit I am referring to is at post : https://www.electronicspoint.com/threads/designing-a-time-delayed-relay.268425/
I realize it's a bit long, if I get a chance maybe I can break it down into a block diagram.

henry barbera

Oct 2, 2014
20
Hi Henry, I am working with Kris on something that maybe able to be repurposed for your needs. I am at the stage of re-checking the board layout before sending it off for production. The device that Kris has helped me extensively with (Thanks!!) is used to sense when there is current flowing in a circuit, when sensed it turns on another device. In your case I think we can program the mcu to your predetermined shutoff level and have the signal sent to another relay to break your circuit and setup a subroutine to reconnect the circuit after 15 minutes, etc. We need to think about a safety relay as well that separates the grid from this device if it senses no input from the grid. For instance, the current circuit I have works off of mains, so if we use a relay that is N.O., while power is on keeping the relay contacts closed, when grid power fails, the relay will go open, isolating the grid from the circuit. Safety for the repair crews to prevent backfeeding and shock. I haven't had a chance to look over the entire previous posts you made, but did see some of it earlier in the week. The circuit I am referring to is at post : https://www.electronicspoint.com/threads/designing-a-time-delayed-relay.268425/
I realize it's a bit long, if I get a chance maybe I can break it down into a block diagram.
thanks for the post! currently if i set it up the new way i have spoke about then i'm only dealing with the one circuit which will open for fifteen minutes it if the load exceeds the set amperage then return to the closed position and wait for the amperage spikes to fade after the compressor and air handler start-up and then begin to read the amps again. so in my case i'm only dealing with the one circuit at 120. i see your kind of where i was in that you want to control one circuit by another.

chopnhack

Apr 28, 2014
1,575
currently i'm only dealing with the one circuit which will open for fifteen minutes it if the load exceeds the set amperage then return to the closed position and wait for the amperage spikes to fade after the compressor and air handler start-up and then begin to read the amps again. i see your kind of where i was in that you want to control one circuit by another.

I reread some of the original post. The diagram of what you are dealing with did clarify things, thanks for that. Working with what you have, would you be able to conveniently splice a connection in series with the three PV grids? That would eliminate the need for clamp on meters. The board I am working on has a hall sensor (same as what @Arouse1973 mentioned) that continuously monitors current. The sensor is fed by a connector that will allow easy wire connections to the outside world. I read the other thread and if I understand correctly - the backfeed issue is mitigated by whether the AC is running or not? If the AC is off and mains power is on, your PV grid's power doesn't pass to the house. If the mains is on and AC is on and you have a surplus then the power would pass into the household.

@KrisBlueNZ - perhaps a pot on one of the input pins of the PIC to allow the end user easy access to changing the current levels at which the action is taken instead of having to reprogram the chip.

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Yeah. If he only wants to monitor one current flow, he could omit the second Allegro chip and feed a pot into the PIC input that was previously used for that Allegro chip.

I'm afraid I'm not really clear on what he wants. Perhaps one of you guys will produce a block diagram at some stage to clarify the requirements.

henry barbera

Oct 2, 2014
20
Yeah. If he only wants to monitor one current flow, he could omit the second Allegro chip and feed a pot into the PIC input that was previously used for that Allegro chip.

I'm afraid I'm not really clear on what he wants. Perhaps one of you guys will produce a block diagram at some stage to clarify the requirements.
yes - the new way is to monitor only one current and if that current exceeds a certain level then break the current and wait 15 minutes then go back to monitoring the current. thats all i want.

chopnhack

Apr 28, 2014
1,575
Perhaps one of you guys will produce a block diagram at some stage to clarify the requirements.
@henry barbera Does this sum up your existing installation?

Three arrays of three cells, each feeding a microinverter. The microinverter's AC output is fed into wall outlets which more than likely where installed by the electrician or yourself to be on the same circuit or breaker as your AC system. When the sun shines, the power produced by the array is fed to the A/C compressor via the contactor. If power fails, the inverters themselves are responsible for prevention of islanding - their internal circuitry senses AC loss and stop inverting.

There is a flaw in the connection to the control unit below. Perhaps others can chime in and help reroute it. I am getting a little hung up on the fact that the ouput of the inverters is also the input of the same - i.e. the inverters plug into standard outlets to back feed power into the power grid, but they also use some of the mains energy to sense when the grid is up or down, that is the anti-islanding effect. Further, Henry stated that his system does not produce enough energy to completely power the A/C which means that his mains must be in series with his array to allow it to run. This means that the PV output and the mains input both need to be on a common run to the relay that will cut them off - however, in cutting them off, the inverter will think the grid is offline. Will that be an issue?

Last edited:

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
What's the thing at the bottom, centre-right?

chopnhack

Apr 28, 2014
1,575
What's the thing at the bottom, centre-right?
Sorry, didn't label that one - wall outlets, mains outlets.
Edit: Fixed images

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Sorry to be difficult... could you put arrows on the lines in the bottom section please?

Fish4Fun

So long, and Thanks for all the Fish!
Aug 27, 2013
472
Hey Henry!

It looks like you are in good hands, so I am not going to attempt to side-track your current path too much...but as you have been re-thinking this, and it is obviously very important to you...I still think you might consider a slightly different approach....

If you define some value of consumption from the mains as a "minimum threshold" below which you consider it economically viable to run the AC units then you can eliminate a great deal of complicated logic design and expensive sensors....and simply use the AC unit's existing thermostat functions to control it...if these are "analog window units" then you could easily add thermostats with the appropriate hysteresis and control features....So this assumes that you can access a standard HVAC "Call For Heat/Cool" output line AND that you install some type of inexpensive current sensor onto your Mains feed....

Psuedo Code or Hard Wired Logic

Code:
Loop:
If Manual Overide = False then
If Real Time Clock > 08:00 AND Real Time Clock < 18:00 then
If Lockout_Timer = False then
If Mains Current > XH Amps then
Set HVAC Call For Heat/Cool Output = False
Set Lockout_Timer = MinOffTime
Go To Loop
End If
If Mains Current < XL Amps then
Set HVAC Call For Heat/Cool Output = HVAC Call For Heat/Cool Input
Set Lockout_Timer = MinOnTime
Go To Loop
Else
Go To Loop
End If
Else
Go To Loop
End If
End If
End if
Set HVAC Call For Heat/Cool Output = HVAC Call For Heat/Cool Input
Go To Loop

At the end of the day you want to minimize your grid consumption and utilize as much of your PV generated power as possible, you don't really care if you keep the house @ 60F during the day, but if you aren't using the PV generated power for other things, then there is no "harm" in running the AC units....You just don't want them to run excessively if you have to supply them with grid power....

By using off-the-shelf or already installed standard HVAC thermostats you can simply "hi-jack" their functionality when for whatever reason your grid demand exceeds a certain "set point"....You can restore their functionality when the grid consumption drops below a second set point, OR you manually over-ride the "hi-jacking" function. Most modern thermostats have a built in compressor delay, and most newer AC untis have a built-in compressor delay....AND you can add "extra" delays into your logic model....

As far as actually implementing the logic, you can use dedicated logic devices, a micro controller or even a PC....this part is fairly simple, the important part is that we define the various "inputs" (ie: Gird Usage, Time Of Day, Need For Cooling Etc....and define appropriate sensors) to determine if you want to allow "normal functionality" or "interrupt normal functionality" of a standard thermostat.....In your case you might want to set the thermostat on your smaller AC unit to 60F and the thermostat on your larger AC unit to 65F thus ensuring they would "generally" be on unless their normal functionality was "hi-jacked' by the above logic...As far as setting the "current trip points", if we assume that the smaller AC unit consumes 2A @ 220V and the larger unit consumes 3A @ 220V and your "normal consumption" with both units off is ~2A then you might set the "on" trip point for the smaller unit @1A. In this case the smaller unit would be "allowed" to turn on during the defined period any time the power consumption dropped below 1A....it would then run for the "minimum on time" (perhaps 10 minutes) before the current consumption was again checked....if the grid consumption 10 minutes later was below the "high" threshold, say 1.5A then the unit would continue to run. If the larger unit had a low current threshold of say 0.5A then it would not turn on until after the smaller unit was already running and if it had a "high threshold" of say 2A of mains consumption then the smaller unit would "drop out" first and the larger unit would continue to run until the mains consumption exceeded 2A.....Obviously the thresholds and set points would need to be adjusted for actual usage, and if you are using 120V units on a 240V grid then current sensing and load balancing will make the current sensing set-up more complicated, but the approach is still viable...assuming it is what you actually want.

OK, so i went into a bit more detail than I was planning when i started, but I really think you should consider this approach....It is a very close approximation to "what you do intuitively when you are home"...and perhaps a bit better;-) If the various automated appliances in your home "turn on" and start using grid power, or if a "cloud" comes over and decreases your PV generated power then your grid consumption increases...by sensing the grid consumption and selectively turning your AC units on/off you can minimize your grid consumption and maximize your PV consumption...and I think this is your goal.

Fish

Edit: Hrmm, all of the "white space" in between the "code tags" vanished....it was a lot easier to follow with the white space, lol. Not much I can do about that :-(

Edit #2: I am going to be peeved if the manually added white space doesn't "stick", lol. Kris, don't know if you know the code writer well, but it should be fairly easy to exclude the code tags from the general white space stripping function.....It really takes ALL the fun out of HAVING code tags if you can't C&P code with white space....I would consider that a fairly major flaw worthy of fixing...obviously...IMHO, lol.

Last edited:

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Hrmm, all of the "white space" in between the "code tags" vanished....it was a lot easier to follow with the white space, lol. Not much I can do about that :-(
Actually, you can put it back in, if you can be bothered. It was stripped out when you pasted the text into your post. It's a very irritating "feature" of the XenForo system. I've reported it to Ian. There's no guarantee it will ever be fixed though.

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