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Solid State Relay vs Mechanical Relay

Equipment Power Supply Remote Astrophotography
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Daniel Carter avatar
Daniel Carter avatar
I have an electronics question for everyone. I have a Moravian C5-100M camera that I am planning on installing on my remote 12.5" iDK to replace a C3-61000 camera. However, the new  camera can draw over 6 amps when cooling.

I have a UPBv3 to control everything on my telescope and the switchable power outlets on the UPBv3 will power down the outlets if the combined output is above 6 amps. So, I am unable to use one of the normal 12v switchable outlets for powering the camera.

One workaround that is available is to use one of the always on ports on the UPBv3 which will provide up to 8 amps. However, I want to be able to switch the power on and off using the UPBv3. This brings me to my question about relays. I plan on using one of the switchable power outlets to power a relay board and provide the power to the camera through one of the always on ports. That allows me to use the switchable outlet to turn the relay on and off and provide the power to the camera through the always on port.

I have found several DC-DC solid state relays as well as the DC 12V mechanical relays. Is there a benefit over using one over the other for this application? I like the idea of a SSR since there are no moving parts. The observatory is in a somewhat dusty area so I was concerned about the mechanical relay failing.

Thanks in advance!
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Dark Matters Astrophotography avatar
Dark Matters Astrophotography avatar
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?
Reg Pratt avatar
Reg Pratt avatar
Dark Matters Astrophotography:
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?

This. It's a far simpler solution to just use a web power switch to manage the cameras power separately from the UPB.
John Hayes avatar
John Hayes avatar
Dark Matters Astrophotography:
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?

I completely agree with Bill here.  That's how I control everything on my scopes.

John
Daniel Carter avatar
Daniel Carter avatar
Dark Matters Astrophotography:
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?

I may end up using the DLI I already have on site.

I already have the mount in place (and all the wires currently ran through the mount) and would prefer the cable to be ran through the AP1600. It is easier to go the relay route and use the UPBv3 since everything is already installed and I am just replacing the camera. The power supply that came with the camera (I am the second owner and not sure if the power brick that I have is original) is pretty short as well which makes things a bit more difficult.
Daniel Carter avatar
Daniel Carter avatar
John Hayes:
Dark Matters Astrophotography:
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?

I completely agree with Bill here.  That's how I control everything on my scopes.

John

I have the DLI switch on site and use it for a number of things already. Since I wanted the cables ran through the mount I was trying to find an alternative solution using a relay.
Dark Matters Astrophotography avatar
Dark Matters Astrophotography avatar
Daniel Carter:
Dark Matters Astrophotography:
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?

I may end up using the DLI I already have on site.

I already have the mount in place (and all the wires currently ran through the mount) and would prefer the cable to be ran through the AP1600. It is easier to go the relay route and use the UPBv3 since everything is already installed and I am just replacing the camera. The power supply that came with the camera (I am the second owner and not sure if the power brick that I have is original) is pretty short as well which makes things a bit more difficult.



i use a powerwerx adjustable power supply and this 4 pin adapter to switch a 2.1 x 5.5 connector to the 4 pin for the camera.

https://www.amazon.com/gp/aw/d/B0B39J7D39?psc=1&ref=ppx_pop_mob_b_asin_title

Everything but this adapter can be obtained from Powerwerx. Very solid setup with clean power. I don’t use the brick they ship with the camera at all.
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Daniel Carter avatar
Daniel Carter avatar
Dark Matters Astrophotography:
Daniel Carter:
Dark Matters Astrophotography:
Just curious why you wouldn’t use a DLI switch to power the camera and just use that to power it on and off remotely?

I may end up using the DLI I already have on site.

I already have the mount in place (and all the wires currently ran through the mount) and would prefer the cable to be ran through the AP1600. It is easier to go the relay route and use the UPBv3 since everything is already installed and I am just replacing the camera. The power supply that came with the camera (I am the second owner and not sure if the power brick that I have is original) is pretty short as well which makes things a bit more difficult.



i use a powerwerx adjustable power supply and this 4 pin adapter to switch a 2.1 x 5.5 connector to the 4 pin for the camera.

https://www.amazon.com/gp/aw/d/B0B39J7D39?psc=1&ref=ppx_pop_mob_b_asin_title

Everything but this adapter can be obtained from Powerwerx. Very solid setup with clean power. I don’t use the brick they ship with the camera at all.

I already have the 2.1x5.5 adapter that you linked - I was planning on using it along with the relay. It has worked well in my limited testing here at home. Someone on the CN forum had posted a similar adapter on the C5-100M thread.

I may end up just using a Powererx type power supply and run a new cable through the mount (the ones I have for my UPBv3 and mount are made by Astron). I was trying to avoid having to run another cable through the mount since everything is already in place.
Tony Gondola avatar
Tony Gondola avatar
To answer the original question I think you'll find that a solid state relay will be much more reliable in that environment. Electromagnetic relays tend to be a lot less reliable although they can carry extremely large loads. I wouldn't think that would be an issue in your application.
Dark Matters Astrophotography avatar
Dark Matters Astrophotography avatar
Daniel Carter:
I already have the 2.1x5.5 adapter that you linked - I was planning on using it along with the relay. It has worked well in my limited testing here at home. Someone on the CN forum had posted a similar adapter on the C5-100M thread.

I may end up just using a Powererx type power supply and run a new cable through the mount (the ones I have for my UPBv3 and mount are made by Astron). I was trying to avoid having to run another cable through the mount since everything is already in place.




Probably Roberto as he is the one that told me about it via email.

While you are still in the planning phase, do plan to run USB2 for the camera instead of USB3. We have a C5A-100M that is having a strange issue with the shutter not opening prior to imaging. We suspect the USB3 run that was in place at the time the site set it up to be the culprit. I will not know for sure until later this evening, but I can say that I ran a single USB2 through my 1100 mount to get a direct connection from the C5 to the PC. I have not experienced this shutter issue or others that folks have noted.
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adon avatar
adon avatar
The Moravian C5-100M says 60W at maximum cooling so 5 A at 12 V. 1 amp buffer on the switchable ports should be enough as the UPBv3 specs say 6 A each. I had some issues, with the UPBv3 cutting out using a non-OEM power supply. When I switched to the Pegasus 10A PSU the problems went away.

Otherwise I would use a 10A solid state relay, and switch it using the 5 V buck output (depending on the relay). This should be reliable.

Are you in a location where you need max cooling? If you set the minimum cooling time (in NINA for example) to a longer duration you could prevent the cooler from drawing max power during the initial cooling. Then, if you are not setting the lowest possible temperature and you are not in an excessively hot location, maybe you can avoid needing max power - at least as a stop-gap measure.
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Daniel Carter avatar
Daniel Carter avatar
The Moravian C5-100M says 60W at maximum cooling so 5 A at 12 V. 1 amp buffer on the switchable ports should be enough as the UPBv3 specs say 6 A each. I had some issues, with the UPBv3 cutting out using a non-OEM power supply. When I switched to the Pegasus 10A PSU the problems went away.

Otherwise I would use a 10A solid state relay, and switch it using the 5 V buck output (depending on the relay). This should be reliable.

Are you in a location where you need max cooling? If you set the minimum cooling time (in NINA for example) to a longer duration you could prevent the cooler from drawing max power during the initial cooling. Then, if you are not setting the lowest possible temperature and you are not in an excessively hot location, maybe you can avoid needing max power - at least as a stop-gap measure.

I am powering the UPBv3 with a power supply rated at 25 amps so power shouldn't be an issue. My power supply has dual powerpole connectors so I will most likely run another cable through the mount to power the C5. I think that will be the most stable solution instead of using the regulated output to switch a relay which is powered from the Always On plug from the UPBv3.

I know of at least one person who had issues powering their camera directly with the UPBv3 regulated output port. The regulated outputs are 6A max output and this user experienced the camera drawing more than 60 watts causing UPBv3 to power down that port. I'm not sure if that is a common issue but it is one that I wish to avoid.

It will be setup on my iDK out in southern New Mexico so it does get pretty warm during the summer there.
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Daniel Carter avatar
Daniel Carter avatar
Dark Matters Astrophotography:
Probably Roberto as he is the one that told me about it via email.

While you are still in the planning phase, do plan to run USB2 for the camera instead of USB3. We have a C5A-100M that is having a strange issue with the shutter not opening prior to imaging. We suspect the USB3 run that was in place at the time the site set it up to be the culprit. I will not know for sure until later this evening, but I can say that I ran a single USB2 through my 1100 mount to get a direct connection from the C5 to the PC. I have not experienced this shutter issue or others that folks have noted.

That is an odd issue with USB cables. Is it just the one cable giving issues or any USB3 cable?
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Dark Matters Astrophotography avatar
Dark Matters Astrophotography avatar
Daniel Carter:
Dark Matters Astrophotography:
Probably Roberto as he is the one that told me about it via email.

While you are still in the planning phase, do plan to run USB2 for the camera instead of USB3. We have a C5A-100M that is having a strange issue with the shutter not opening prior to imaging. We suspect the USB3 run that was in place at the time the site set it up to be the culprit. I will not know for sure until later this evening, but I can say that I ran a single USB2 through my 1100 mount to get a direct connection from the C5 to the PC. I have not experienced this shutter issue or others that folks have noted.

That is an odd issue with USB cables. Is it just the one cable giving issues or any USB3 cable?



Not sure at this point. USB3 is finicky and I avoid it at all costs unless the line for it is amplified. 

Another possible gotcha is not to supply the camera with too much voltage. It will not operate properly if you do that. I tried one of those 14.1v Powerwerx boxes and that had too much juice. Had to switch to the adjustable one.
Daniel Carter avatar
Daniel Carter avatar
Dark Matters Astrophotography:
Not sure at this point. USB3 is finicky and I avoid it at all costs unless the line for it is amplified. 

Another possible gotcha is not to supply the camera with too much voltage. It will not operate properly if you do that. I tried one of those 14.1v Powerwerx boxes and that had too much juice. Had to switch to the adjustable one.

I'll be sure to take a USB2 cable when I visit to install.

The Astron power supply puts out 13.8V so I may have to invest in a variable voltage power supply. I can open the case of the Astron power supply and it can be adjusted +/- 1V. So, I could dial it down at 12.8V according to the spec sheets. I may just opt for the more easily adjustable power supply to make things easier.
Dark Matters Astrophotography avatar
Dark Matters Astrophotography avatar
Daniel Carter:
I'll be sure to take a USB2 cable when I visit to install.




Good idea as that change seems to have fixed the shutter issue. Could have just been a bad USB3 cable as well, but USB2 is always the better option if you don't need the speed of USB3.
Médéric Hébert avatar
Médéric Hébert avatar
Are you using the relay on the UPBv3? You could use that instead.
Dave Erickson avatar
Dave Erickson avatar
I have used both electro-mechanical and solid state relays for more than a decade, in a rather harsh remote - solar powered environment. Both have performed with little issue in high current and low current remote control switching applications. There have been failures of both, solid state relays tend to fail in the "ON" state and electro-mechanical relays tend to fail in the "OFF" state. For this reason I prefer electro-mechanical relays, better to fail off than on...

Here is a link to a presentation for design and construction of a remote control system for a CDK17 in a 10' dome, it outlines a design consideration for SSR's on page 16:

https://cdn.astrobin.com/ckeditor-files/14617/2023/7731b0ae-eeca-46ff-aa72-8a804642acf7.pdf
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Tony Gondola avatar
Tony Gondola avatar
The result in one application doesn't say much. You need to look at the MTBF (mean time between failure) or MCBF (mean cycles before failure) for your selected relay to help you make the right choice.
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