Autmoating Sprinklers with M1

[RandyKnight]

You could use M1RB by themselves with XOV. I don't have XOV, just RB's. For your sprinkler valves you need the relays, not just outputs.

So here's my question. I know this is true as I've been told many times, but I don't know WHY. If the wall wart is providing the power, why can't you just use the output to complete the circuit? I just bench tested this (got my bus issues figured out) and it seems to work. I end up with ~28VAC when the output is on ... no relay. So what's the issue with doing it this way?

 

[BraveSirRobbin]

So here's my question. I know this is true as I've been told many times, but I don't know WHY. If the wall wart is providing the power, why can't you just use the output to complete the circuit? I just bench tested this (got my bus issues figured out) and it seems to work. I end up with ~28VAC when the output is on ... no relay. So what's the issue with doing it this way?

I'm not gettin ya Randy! Are you saying you want to use the outputs of the Elk expansion boards (and not the relay)? Are you saying you want to use the wall wart that you had for the old sprinkler controller (24 volts AC)?

I don't see how you can use the 24 volts AC wall wart supply without the relays, but maybe I'm not understanding the question.

 

[RandyKnight]

So here's my question. I know this is true as I've been told many times, but I don't know WHY. If the wall wart is providing the power, why can't you just use the output to complete the circuit? I just bench tested this (got my bus issues figured out) and it seems to work. I end up with ~28VAC when the output is on ... no relay. So what's the issue with doing it this way?

I'm not gettin ya Randy! Are you saying you want to use the outputs of the Elk expansion boards (and not the relay)? Are you saying you want to use the wall wart that you had for the old sprinkler controller (24 volts AC)?

I don't see how you can use the 24 volts AC wall wart supply without the relays, but maybe I'm not understanding the question.

This is from memory since I'm at work now but here's what I did last night on the bench.

Hooked up the Output 1 of the output expander (Output 17 on the Elk) to the 912 and the Wall Wart like in this schematic you helpfuly provided. I didn't have it hooked up to a valve but I just used a multimeter to check voltage on the lines that would be goin to the valve. Everything worked great.

So then I got thinking, if the output lead has no voltage when it's off, and all it's doing is tripping the relay, and the power comes from the other side of the relay, why do you need the relay. So I took the relay out of the mix as follows:

Wall Wart Lead 1 ---> Valve
Output Lead ---> Valve
Output Negative Lead ---> Wallwart Lead2


I "think" that's right. Hard to describe without a drawing. At the end of the day, the 24v power wouldn't make it to the valve if the output was off. But if I turned the ouput on, I got 24V on the leads going to the valve.

Does that make any more sense?

So my question is if I can get 24V that way, why do I need a relay?

 

[RandyKnight]

So here's my question. I know this is true as I've been told many times, but I don't know WHY. If the wall wart is providing the power, why can't you just use the output to complete the circuit? I just bench tested this (got my bus issues figured out) and it seems to work. I end up with ~28VAC when the output is on ... no relay. So what's the issue with doing it this way?

I'm not gettin ya Randy! Are you saying you want to use the outputs of the Elk expansion boards (and not the relay)? Are you saying you want to use the wall wart that you had for the old sprinkler controller (24 volts AC)?

I don't see how you can use the 24 volts AC wall wart supply without the relays, but maybe I'm not understanding the question.

This is from memory since I'm at work now but here's what I did last night on the bench.

Hooked up the Output 1 of the output expander (Output 17 on the Elk) to the 912 and the Wall Wart like in this schematic you helpfuly provided. I didn't have it hooked up to a valve but I just used a multimeter to check voltage on the lines that would be goin to the valve. Everything worked great.

So then I got thinking, if the output lead has no voltage when it's off, and all it's doing is tripping the relay, and the power comes from the other side of the relay, why do you need the relay. So I took the relay out of the mix as follows:

Wall Wart Lead 1 ---> Valve
Output Lead ---> Valve
Output Negative Lead ---> Wallwart Lead2


I "think" that's right. Hard to describe without a drawing. At the end of the day, the 24v power wouldn't make it to the valve if the output was off. But if I turned the ouput on, I got 24V on the leads going to the valve.

Does that make any more sense?

So my question is if I can get 24V that way, why do I need a relay?

The outputs on the standard Elk Output expander are rated for a very small current (check the specification sheet). For heaver loads or when a different voltage level (or AC voltage) is desired, you can drive a conventional or solid state relay (with a rating high enough for the desired load) from the Elk output and let the relay switch the larger load. Another option would be to use the Elk output expander with the onboard relays. With any wiring, personal safety and proper wiring procedures are of upmost importance, particuliarly if higher voltages are involved. National and local codes should be observed. If there are any doubts, one should seek professional help.

Brian

So in my 2nd scenario, if the valve was actually connected, the current would damage the ouptut expander and/or M1?

 

[BDHall]

So here's my question. I know this is true as I've been told many times, but I don't know WHY. If the wall wart is providing the power, why can't you just use the output to complete the circuit? I just bench tested this (got my bus issues figured out) and it seems to work. I end up with ~28VAC when the output is on ... no relay. So what's the issue with doing it this way?

I'm not gettin ya Randy! Are you saying you want to use the outputs of the Elk expansion boards (and not the relay)? Are you saying you want to use the wall wart that you had for the old sprinkler controller (24 volts AC)?

I don't see how you can use the 24 volts AC wall wart supply without the relays, but maybe I'm not understanding the question.

This is from memory since I'm at work now but here's what I did last night on the bench.

Hooked up the Output 1 of the output expander (Output 17 on the Elk) to the 912 and the Wall Wart like in this schematic you helpfuly provided. I didn't have it hooked up to a valve but I just used a multimeter to check voltage on the lines that would be goin to the valve. Everything worked great.

So then I got thinking, if the output lead has no voltage when it's off, and all it's doing is tripping the relay, and the power comes from the other side of the relay, why do you need the relay. So I took the relay out of the mix as follows:

Wall Wart Lead 1 ---> Valve
Output Lead ---> Valve
Output Negative Lead ---> Wallwart Lead2


I "think" that's right. Hard to describe without a drawing. At the end of the day, the 24v power wouldn't make it to the valve if the output was off. But if I turned the ouput on, I got 24V on the leads going to the valve.

Does that make any more sense?

So my question is if I can get 24V that way, why do I need a relay?

The outputs on the standard Elk Output expander are rated for a very small current (check the specification sheet). For heaver loads or when a different voltage level (or AC voltage) is desired, you can drive a conventional or solid state relay (with a rating high enough for the desired load) from the Elk output and let the relay switch the larger load. Another option would be to use the Elk output expander with the onboard relays. With any wiring, personal safety and proper wiring procedures are of upmost importance, particuliarly if higher voltages are involved. National and local codes should be observed. If there are any doubts, one should seek professional help.

Brian

So in my 2nd scenario, if the valve was actually connected, the current would damage the ouptut expander and/or M1?

The Elk outputs are approx 12vdc @50ma. An ordinary sprinkler valve would require more current than this and likely a different voltage as well. My sprinkler valves are designed for 24 vac. One of the Elk relay board or relay expander options can be a pretty handy way to hook up sprinkler valves when used in conjunction with a properly sized, current limited output wall wart to supply the power for the valves.

Brian

 

[RandyKnight]

The Elk outputs are approx 12vdc @50ma. An ordinary sprinkler valve would require more current than this and likely a different voltage as well. My sprinkler valves are designed for 24 vac. One of the Elk relay board or relay expander options can be a pretty handy way to hook up sprinkler valves when used in conjunction with a properly sized, current limited output wall wart to supply the power for the valves.

But in this case the current and voltage are coming from the wall wart, not the M1. All the output would be used for is to complete the circuit. I'm sure what you're saying is right ... I just don't get the why.

 

[ckindt]

The Elk outputs are approx 12vdc @50ma. An ordinary sprinkler valve would require more current than this and likely a different voltage as well. My sprinkler valves are designed for 24 vac. One of the Elk relay board or relay expander options can be a pretty handy way to hook up sprinkler valves when used in conjunction with a properly sized, current limited output wall wart to supply the power for the valves.

But in this case the current and voltage are coming from the wall wart, not the M1. All the output would be used for is to complete the circuit. I'm sure what you're saying is right ... I just don't get the why.

Sorry to jump in, but the limiting part (at least) is the output transistor in the elk. If you don't use a relay, you will most likely overload your elk's transistor when your sprinkler solenoid coil draws electrical current in excess of the specs on the elks outputs. The current from your wallwart flows through the collector and emitter of the output transistor then on to the solenoid.

Please use a relay(s). This way your elk's transistor is only exposed to the small electrical current drawn by the relay's coil*. The contact on the relay is rated to withstand higher current (compare to specs of your sprinkler solenoid) and since it is completely isolated, it can handle an entirely different power source too.

* check relay specs too - use a relay with a coil that draws less than 50mA and you should buy one that has voltage suppression too - this will further protect the elks outputs from the brief high voltage that is released from the coil every time it is de-energized. If you want LEDs, you can get relays with built-in LEDs to monitor the coil status.

In your test, your multimeter uses much less current than your sprinkler solenoid does. This is why no harm was done and it's probably good you didn't hook it up to your solenoid.

 

[RandyKnight]

The Elk outputs are approx 12vdc @50ma. An ordinary sprinkler valve would require more current than this and likely a different voltage as well. My sprinkler valves are designed for 24 vac. One of the Elk relay board or relay expander options can be a pretty handy way to hook up sprinkler valves when used in conjunction with a properly sized, current limited output wall wart to supply the power for the valves.

But in this case the current and voltage are coming from the wall wart, not the M1. All the output would be used for is to complete the circuit. I'm sure what you're saying is right ... I just don't get the why.

Sorry to jump in, but the limiting part (at least) is the output transistor in the elk. If you don't use a relay, you will most likely overload your elk's transistor when your sprinkler solenoid coil draws electrical current in excess of the specs on the elks outputs. The current from your wallwart flows through the collector and emitter of the output transistor then on to the solenoid.

Please use a relay(s). This way your elk's transistor is only exposed to the small electrical current drawn by the relay's coil*. The contact on the relay is rated to withstand higher current (compare to specs of your sprinkler solenoid) and since it is completely isolated, it can handle an entirely different power source too.

* check relay specs too - use a relay with a coil that draws less than 50mA and you should buy one that has voltage suppression too - this will further protect the elks outputs from the brief high voltage that is released from the coil every time it is de-energized. If you want LEDs, you can get relays with built-in LEDs to monitor the coil status.

In your test, your multimeter uses much less current than your sprinkler solenoid does. This is why no harm was done and it's probably good you didn't hook it up to your solenoid.

Thanks. That was the answer I was looking for. I knew there was a reason but wanted to know what it was. And I felt pretty safe with the multimeter ... wouldn't have connected the valve that way.

 

[ckindt]

Thanks. That was the answer I was looking for. I knew there was a reason but wanted to know what it was. And I felt pretty safe with the multimeter ... wouldn't have connected the valve that way.

You're welcome - I'm glad to help.

 

[BraveSirRobbin]

Also, the solenoids require 24 volts AC for operation (at least that is their rating for most sprinkler control valves). That is why I listed a 24 volts AC wall wart for use with the relays as the Elk can not supply this voltage with its outputs.