Hello

I have a roll off roof observatory with a 230V gate opening ac motor to open and close the roof. The astronomy equipment 12V and comms is controlled by a Pegasus Power Box Advance which can output a 9V supply, switchable from the software that controls it. I built an Arduino rain sensor that warns me in the event of rain detection so that I can park the telescope to horizontal and close the roof. The roof motor has a pair connected to the control board that opens and closes the roof using a transient short circuit of the pair.

What approach could I take to use the 9V supply to momentarily short the motor control pair to open and close the roof?

Thanks

Graeme

 

Can you define "a transient short circuit"?
What is the time duration?

The standard solution is a 555-timer in monostable mode driving a relay.

 

I would use the an output from the Arduino to activate a relay momentarily to complete the motor connection if this is all thats needed.
The relay module can be powered from the 12 or 9 volt supply.

 

Can you define "a transient short circuit"?
What is the time duration?

The standard solution is a 555-timer in monostable mode driving a relay.

Yes, the time duration would be representative of a manually operated push button switch. I operate the roll off roof locally using a hand held remote control. My intention is to control the motor remotely from indoors on my PC screen.

I used a 555 timer in another project for variable control of a telescope heated dew band. I have a couple more available.

Thanks

Graeme

 

I would use the an output from the Arduino to activate a relay momentarily to complete the motor connection if this is all thats needed.
The relay module can be powered from the 12 or 9 volt supply.

I did think of doing it using an Arduino but it seemed like over kill! But perhaps not.

The main consideration would be that the relay must fail to open circuit to fail safe. If the observatory roof were to close while the telescope was in use it would cause expensive damage.

Thanks

Graeme

 

I did think of doing it using an Arduino but it seemed like over kill! But perhaps not.

The main consideration would be that the relay must fail to open circuit to fail safe. If the observatory roof were to close while the telescope was in use it would cause expensive damage.

Thanks

Graeme

My suggestion is using the same Arduino that you are using with the rain sensor.
Have sensors or limit switches to detect if the roof is open and when closed as feedback for the Arduino.

 

I did think of doing it using an Arduino but it seemed like over kill! But perhaps not.

The main consideration would be that the relay must fail to open circuit to fail safe. If the observatory roof were to close while the telescope was in use it would cause expensive damage.

Thanks

Graeme

That's easy. Power to the roof motor must go through a cut-out switch if the telescope is not in the parked position. Hard wired - no logic required.

 

I operate the roll off roof locally using a hand held remote control.

Does the roof motor have limit switches?

 

Thanks again.

Yes, I could use the same Arduino as the rain sensor. But there is room in the observatory control panel for an additional Arduino and relay. The rain sensor uses an ASCOM safety monitor driver that displays status on the screen within the astrophotography software, NINA. And that generates a notification that is sent to my phone, using Pushover to wake me up if I nod off while capturing astro photons.

There is a limit switch on the motor control panel that stops the motor when the roof reaches fully open and closed. I can see what is happening on the security camera and I am reticent to automate the roof closure upon rain detection because of the potential for damage to the telescope. In the event of rain detection, I park the telescope with a click of the mouse from indoors, I am happy to be part of the feed back loop! But I have to go out to close the roof which causes a delay.

My aim is to watch the camera to confirm the telescope is horizontal and then click the PPBA 9V supply to operate the roof. So if I use an Arduino to detect the 9V and send a pulse to the relay to short the pair to the motor control panel, that should work ok.

Is there any risk that a power cut or surge would cause the Arduino to pulse the relay?

 

Is there any risk that a power cut or surge would cause the Arduino to pulse the relay?

Accidentally!

 

There is always a chance that something goes wrong.
A motor power lockout is your final line of defence.

 

Hello

I have a roll off roof observatory with a 230V gate opening ac motor to open and close the roof. The astronomy equipment 12V and comms is controlled by a Pegasus Power Box Advance which can output a 9V supply, switchable from the software that controls it. I built an Arduino rain sensor that warns me in the event of rain detection so that I can park the telescope to horizontal and close the roof. The roof motor has a pair connected to the control board that opens and closes the roof using a transient short circuit of the pair.

What approach could I take to use the 9V supply to momentarily short the motor control pair to open and close the roof?

Thanks

Graeme

IRLZ44N FET

 

Accidentally!

Like MrChips mentioned, a switch that is closed only when the scope is parked that would then send 12 volts to the relay circuit but only activated by your PPBA 9v signal.
How long does the relay need to be activated to fully close the roof?

 

What if the relay is stuck in the closed position?

I have been thinking about this. Now you can have triple redundancy.
1) a high current switch that supplies power to the motor,
2) a separate low current switch that supplies power to the relay,
3) logic controller that enables the relay driver.

 

It appears that the motor control pair of wires is for opening and closing with just a momentary closure.
Need the TS to confirm this.
I understand the concern by the TS when the scope is parked and the roof is closed a "glitch" in the logic controller could happen that would open the roof.
So possible a third switch that opens when the roof is fully closed to disable the relay circuit in some manner.