KeepItSimpleStupid
- Joined Mar 4, 2014
- 5,088
Ok briefly:
1. You need an SPDT limit switch that will survive in a greenhouse environment and you don't want it to fail.
Example: https://www.motionsolutions.net/sto...s/omron/SHL_Datasheet_EN_201311_CMS_E_4_1.pdf
2. How fast the motor stops depends on a lot of things. RPM for one. Type of gearing.
3. When a DC motor is turned off, it acts as a generator until it coasts to a stop.
4. If you make that generator operate into a short circuit, it stops really quickly. So, in reality you can assume the voltage of the motor and the winding resistance to be max current. I=12/Rm. 30 -40 Amps is a typical automotive relay. The coils are about 150 mA @ 12 V (ball park). The limit switch has to handle about 150 mA inductive.
5, The motor will stop even quicker if the distance between the motor and the relay is small. So, don't make it 50 feet,
6. The relay has a finite operating time in mS.
7. To a lesser extent friction might change with temperature.
8. Yes, the limit switches are momentary.
9. The automotive relays are designed to mount terminals down.
10, you need two limit switches and two automotive relays..
11. Open/close state is optional.
e.g.
00 in between
01 open
10 closed
11 fault
12. Motor running is optional output
And then "What happens if the limit switch fails"? Fuse, breaker, electronic controls etc.
==
I don't have crystal ball and I can't see all of the options. A WIFI web browser was a "suggestion"
e.g. nearest structure with power and WIFI. Ethernet underground may open up other options.
Say POE or some 12 v power limited under ground source
A directional antenna e.g. https://www.motionsolutions.net/sto...s/omron/SHL_Datasheet_EN_201311_CMS_E_4_1.pdf or even a home made one. See: http://antenna-diy.blogspot.com/2008/03/cantenna-part-i-theory.html
it all adds costs, I know. But with two access points you can set up an ethernet to microwave to microwave to Ethernet link between two structures.
==
Again, I don;t know the full extent of the area or what one has to work with, I'm limited. The more I know, the better I can suggest. That said....
Puttng the controller in the workshop might work.
How far is the workshop from the greenhouse with a real wire? Line of sight? WIFI Ethernet in the shop?
Systems exist, look up Modbus TCP, where just the I/O exists close to the location. That system can communicate over Ethernet. Nothing is speed sensitive like computing the RPM of a shaft from interrupts.
Having the controller in your shop might even be a better option. But we may have bigger problems to get that to work.
I, sort of understand that if the design could be as simple as:
1. Open at 6 am, close at dusk (astronomical timer)
2. It's raining or windy close the windows.
3. if the outside temperature is < x close the windows.
4. if the inside temp is >x open the windows.
Hysteresis might be hard to implement. The one sensor (rain, I believe) you linked to apparently resets in a day.
Just a warning; I tend to look at all options no matter how absurd initially just to get stuff on the table.
After it's on the table you can sort it out.
Sometimes if you do the following:
1) What would i want if I had all the time and money in the world.
2) What do I absolutely need.
3) What do I want now.
You can design a system that could be upgraded. Simple things (not for this project) At home, why run CAT5 cables if I only have a 10/100 hub/switch. it might be a tougher decision to run 10G Ethernet at home. Although, I'm in the process of running CAT6 and it could be good to 1000BaseT at lower distances which it would meet.
Telephone will ultimately go over CAT 6 eventually. Adapters force an RJ11 to fit into an RJ45. So, I made the decision to use two colors of cable for CAT6
When I painted a room, I added a dual wall plate and drilled the required holes. No wires yet for telco or TV.
1. You need an SPDT limit switch that will survive in a greenhouse environment and you don't want it to fail.
Example: https://www.motionsolutions.net/sto...s/omron/SHL_Datasheet_EN_201311_CMS_E_4_1.pdf
2. How fast the motor stops depends on a lot of things. RPM for one. Type of gearing.
3. When a DC motor is turned off, it acts as a generator until it coasts to a stop.
4. If you make that generator operate into a short circuit, it stops really quickly. So, in reality you can assume the voltage of the motor and the winding resistance to be max current. I=12/Rm. 30 -40 Amps is a typical automotive relay. The coils are about 150 mA @ 12 V (ball park). The limit switch has to handle about 150 mA inductive.
5, The motor will stop even quicker if the distance between the motor and the relay is small. So, don't make it 50 feet,
6. The relay has a finite operating time in mS.
7. To a lesser extent friction might change with temperature.
8. Yes, the limit switches are momentary.
9. The automotive relays are designed to mount terminals down.
10, you need two limit switches and two automotive relays..
11. Open/close state is optional.
e.g.
00 in between
01 open
10 closed
11 fault
12. Motor running is optional output
And then "What happens if the limit switch fails"? Fuse, breaker, electronic controls etc.
==
I don't have crystal ball and I can't see all of the options. A WIFI web browser was a "suggestion"
e.g. nearest structure with power and WIFI. Ethernet underground may open up other options.
Say POE or some 12 v power limited under ground source
A directional antenna e.g. https://www.motionsolutions.net/sto...s/omron/SHL_Datasheet_EN_201311_CMS_E_4_1.pdf or even a home made one. See: http://antenna-diy.blogspot.com/2008/03/cantenna-part-i-theory.html
it all adds costs, I know. But with two access points you can set up an ethernet to microwave to microwave to Ethernet link between two structures.
==
Again, I don;t know the full extent of the area or what one has to work with, I'm limited. The more I know, the better I can suggest. That said....
Puttng the controller in the workshop might work.
How far is the workshop from the greenhouse with a real wire? Line of sight? WIFI Ethernet in the shop?
Systems exist, look up Modbus TCP, where just the I/O exists close to the location. That system can communicate over Ethernet. Nothing is speed sensitive like computing the RPM of a shaft from interrupts.
Having the controller in your shop might even be a better option. But we may have bigger problems to get that to work.
I, sort of understand that if the design could be as simple as:
1. Open at 6 am, close at dusk (astronomical timer)
2. It's raining or windy close the windows.
3. if the outside temperature is < x close the windows.
4. if the inside temp is >x open the windows.
Hysteresis might be hard to implement. The one sensor (rain, I believe) you linked to apparently resets in a day.
Just a warning; I tend to look at all options no matter how absurd initially just to get stuff on the table.
After it's on the table you can sort it out.
Sometimes if you do the following:
1) What would i want if I had all the time and money in the world.
2) What do I absolutely need.
3) What do I want now.
You can design a system that could be upgraded. Simple things (not for this project) At home, why run CAT5 cables if I only have a 10/100 hub/switch. it might be a tougher decision to run 10G Ethernet at home. Although, I'm in the process of running CAT6 and it could be good to 1000BaseT at lower distances which it would meet.
Telephone will ultimately go over CAT 6 eventually. Adapters force an RJ11 to fit into an RJ45. So, I made the decision to use two colors of cable for CAT6
When I painted a room, I added a dual wall plate and drilled the required holes. No wires yet for telco or TV.