reef-pi :: An opensource reef tank controller based on Raspberry Pi.

[theatrus]

@Ranjib something I am looking at is moving to Centos arm build, lots of reasons but for me is I can freeze thing and just apply security updates for 10 years without all of the software upgrades. Now if new features are needed etc that's a different story but wanted to throw it out there that I'm waiting for Centos 8 userland to be released and will the start poking at getting it working.

If anyone might be interested in the out come let me know and I can post what I find out. I understand since it will be different from the standard raspbian install that I will be kind of on my own but curious to see if it will be something that will work, I use RHEL at work and at home for some servers, some pros and cons but I like the long support cycles since I'm pretty lazy

Note that raspbian targets ARMv6-HF due to the PiZero, which not even Debian upstream targets.

I don’t foresee any problems outside of needing a proper Pi kernel, as there are a number of patches and special configs for it.

 

[Bigtrout]

I have three aqueon pro's 100w but none of them keep in the range that you guys are talking about, mine are all about 1.5 degree swing. I am doing 1 min checks, but they are nowhere near that tight of a range, interesting. Although I do think they are one of the better heaters out there, but heaters in general are not that good.

Tank size may be a factor here...i have a 75gallon. Smaller tanks lose heat faster

 

[b4tn]

Reading the specs on the relays on thia board, it may be a good option for general equipment at 5 amps or less.
It maybe expensive but you get what u pay for with relays

I was thinking the same. I looked all over and cant find a data sheet on the relays. All I could find was a single 5 star review on newegg for the relay bought alone saying it was great. Most of the main stream controllers out there state that their outlets are 5 amp so I would be comfortable running standard equipment on a relay rated for 8.

 

[Bigtrout]

I was thinking the same. I looked all over and cant find a data sheet on the relays. All I could find was a single 5 star review on newegg for the relay bought alone saying it was great. Most of the main stream controllers out there state that their outlets are 5 amp so I would be comfortable running standard equipment on a relay rated for 8.

I cant find a datasheet either...found some more detailed specs...are they zero cross? Makes a difference in the loads that you use with them

 

[b4tn]

I cant find a datasheet either...found some more detailed specs...are they zero cross? Makes a difference in the loads that you use with them

Thats one of the reasons I was looking for the datasheet. If they where Zero cross I would probably order some today.

 

[Ranjib]

Anybody used these at all? Looks like input is 5-12 volts either high or low trigger and they have an 8 amp AC load current.

https://www.amazon.com/Widewing-Cha...d+state+relay&qid=1557410056&s=gateway&sr=8-9

Oooh. Looks very good, thank you for sharing. Thinking where I can use it.

 

[bishoptf]

Note that raspbian targets ARMv6-HF due to the PiZero, which not even Debian upstream targets.

I don’t foresee any problems outside of needing a proper Pi kernel, as there are a number of patches and special configs for it.

Thanks this is good information, did some digging and looks like they are only supporting Armv7 so will keep that in mind and use one of the newer rpi versions. Just means I've got to go out and purchase another rpi.

 

[Ranjib]

@Ranjib something I am looking at is moving to Centos arm build, lots of reasons but for me is I can freeze thing and just apply security updates for 10 years without all of the software upgrades. Now if new features are needed etc that's a different story but wanted to throw it out there that I'm waiting for Centos 8 userland to be released and will the start poking at getting it working.

If anyone might be interested in the out come let me know and I can post what I find out. I understand since it will be different from the standard raspbian install that I will be kind of on my own but curious to see if it will be something that will work, I use RHEL at work and at home for some servers, some pros and cons but I like the long support cycles since I'm pretty lazy

Let me know if you need any help. Karanbir Singh, the centos lead developer/maintainer is a personal friend of mine and I used to use centos exclusively backin the days.
I am not sure though, if it makes sense of Pi. You'll missout on a lot of things, and I am not sure if you really need all those patches. Patches are for those who cant update things, specially stuff like database servers. I also find the distro specific differences less of a vantage point in post systemd world. Unless you are doing something advance with dnf/rpm stuff... what new things centos/rel will bring compared to debian? let alone the fact that all things offical pi is raspbian based

 

[bishoptf]

Let me know if you need any help. Karanbir Singh, the centos lead developer/maintainer is a personal friend of mine and I used to use centos exclusively backin the days.
I am not sure though, if it makes sense of Pi. You'll missout on a lot of things, and I am not sure if you really need all those patches. Patches are for those who cant update things, specially stuff like database servers. I also find the distro specific differences less of a vantage point in post systemd world. Unless you are doing something advance with dnf/rpm stuff... what new things centos/rel will bring compared to debian? let alone the fact that all things offical pi is raspbian based

Wow you know Karanbir that's pretty cool, I've been a long time user for many years, still on the mailing list. My angle is since I'm freshwater there will not be as many features that I probably will be interested in. The thing I like about Centos is that they have long support cycles (10 years) and if I want to just go into maintenance mode, it can run for a long time and just get security updates and I don't have to jump through any major updates, e.g. Jessie to stretch etc. I use Debian a good bit but with version RHEL 8 they have some new interesting things coming along (not that they will matter to reef-pi) and wanted to see if I can get it to work and how much of a pain it is to do it. Not being able to run on a zero is the first con, will see what the other issues I find. Will take them awhile to port it to Centos so it's still early, will be something interesting to play with.

 

[Bigtrout]

BEWARE USING SOLID STATE RELAYS for AC Loads!!!

Beware using solid state relays to switch AC mains voltage if you dont have an electronics/electrical background!!! Yes there are no moving parts to fail, but there are many other design factors to consider for the average user. For this reason I recommend reef pi users stick with good mechanical relays.

If you select the wrong relay it wont be reliable, and could possibly get hot and either fail or start a fire. The second reason that solid state relays can be bad is that they are never really fully off. In the off state they still have a leakage across the load terminals, meaning the load will have some voltage present even when off. With mains AC this could be very unsafe. The third reason I do not recommend them is heat. Because they are a semiconductor conducting electricity, they get warm. SSR larger than 10 amps should have a heat sink.

There are 2 types of AC SSR relays that would commonly be used in our application. Zero-crossing SSR and instant-on SSR. Ill try to explain the two as simply as I can.

Zero cross relays use internal circuitry to turn on only when the ac sine wave voltage crosses the zero point on the sine wave. This is fine for resistive loads such as heaters, and incandescent lights but is one of the worst ways to turn on a highly inductive load like a light ballast, motor or a return pump.
On a highly inductive load, turning the load on at the zero crossing point can cause a current spike of 10 to 40 times the running current of the load. This can cause the ssr to heat up and fail. The same inductive load turned on at the peak of the voltage wave causes little or no such surge.

The second type of ssr is a random or instantaneous on ssr. This type switches on whenever triggered, no matter where the voltage is on the AC sine wave. These are better for inductive loads, and where precise timing is required, but they still are not perfect. The load may still switch on at the zero point, or maybe its at the voltage peak or somewhere in between. Because of this, if a ssr is used for an inductive load, a safety factor should be used. 50 percent is recommended. In other words, an ssr rated at 10 amps should only be used to switch an inductive load of 5 amps.

In short, although they can be very reliable when used properly, there are too many design factors to consider when using a solid state relay.
Selecting the wrong relay may cause premature failure, and possibly a fire.

@Ranjib feel free to link this is you find this helpful to the project.

 

[bishoptf]

BEWARE USING SOLID STATE RELAYS for AC Loads!!!

Beware using solid state relays to switch AC mains voltage if you dont have an electronics/electrical background!!! Yes there are no moving parts to fail, but there are many other design factors to consider for the average user. For this reason I recommend reef pi users stick with good mechanical relays.

If you select the wrong relay it wont be reliable, and could possibly get hot and either fail or start a fire. The second reason that solid state relays can be bad is that they are never really fully off. In the off state they still have a leakage across the load terminals, meaning the load will have some voltage present even when off. With mains AC this could be very unsafe. The third reason I do not recommend them is heat. Because they are a semiconductor conducting electricity, they get warm. SSR larger than 10 amps should have a heat sink.

There are 2 types of AC SSR relays that would commonly be used in our application. Zero-crossing SSR and instant-on SSR. Ill try to explain the two as simply as I can.

Zero cross relays use internal circuitry to turn on only when the ac sine wave voltage crosses the zero point on the sine wave. This is fine for resistive loads such as heaters, and incandescent lights but is one of the worst ways to turn on a highly inductive load like a light ballast, motor or a return pump.
On a highly inductive load, turning the load on at the zero crossing point can cause a current spike of 10 to 40 times the running current of the load. This can cause the ssr to heat up and fail. The same inductive load turned on at the peak of the voltage wave causes little or no such surge.

The second type of ssr is a random or instantaneous on ssr. This type switches on whenever triggered, no matter where the voltage is on the AC sine wave. These are better for inductive loads, and where precise timing is required, but they still are not perfect. The load may still switch on at the zero point, or maybe its at the voltage peak or somewhere in between. Because of this, if a ssr is used for an inductive load, a safety factor should be used. 50 percent is recommended. In other words, an ssr rated at 10 amps should only be used to switch an inductive load of 5 amps.

In short, although they can be very reliable when used properly, there are too many design factors to consider when using a solid state relay.
Selecting the wrong relay may cause premature failure, and possibly a fire.

@Ranjib feel free to link this is you find this helpful to the project.

Great post, lots of good information!

 

[theatrus]

BEWARE USING SOLID STATE RELAYS for AC Loads!!!

Beware using solid state relays to switch AC mains voltage if you dont have an electronics/electrical background!!! Yes there are no moving parts to fail, but there are many other design factors to consider for the average user. For this reason I recommend reef pi users stick with good mechanical relays.

If you select the wrong relay it wont be reliable, and could possibly get hot and either fail or start a fire. The second reason that solid state relays can be bad is that they are never really fully off. In the off state they still have a leakage across the load terminals, meaning the load will have some voltage present even when off. With mains AC this could be very unsafe. The third reason I do not recommend them is heat. Because they are a semiconductor conducting electricity, they get warm. SSR larger than 10 amps should have a heat sink.

There are 2 types of AC SSR relays that would commonly be used in our application. Zero-crossing SSR and instant-on SSR. Ill try to explain the two as simply as I can.

Zero cross relays use internal circuitry to turn on only when the ac sine wave voltage crosses the zero point on the sine wave. This is fine for resistive loads such as heaters, and incandescent lights but is one of the worst ways to turn on a highly inductive load like a light ballast, motor or a return pump.
On a highly inductive load, turning the load on at the zero crossing point can cause a current spike of 10 to 40 times the running current of the load. This can cause the ssr to heat up and fail. The same inductive load turned on at the peak of the voltage wave causes little or no such surge.

The second type of ssr is a random or instantaneous on ssr. This type switches on whenever triggered, no matter where the voltage is on the AC sine wave. These are better for inductive loads, and where precise timing is required, but they still are not perfect. The load may still switch on at the zero point, or maybe its at the voltage peak or somewhere in between. Because of this, if a ssr is used for an inductive load, a safety factor should be used. 50 percent is recommended. In other words, an ssr rated at 10 amps should only be used to switch an inductive load of 5 amps.

In short, although they can be very reliable when used properly, there are too many design factors to consider when using a solid state relay.
Selecting the wrong relay may cause premature failure, and possibly a fire.

@Ranjib feel free to link this is you find this helpful to the project.

Good advice and summary.

Even the commercial units suffer from some of these problems. E.g., the APEX EB8 have two outlets on relays and 6 on triacs (internal SSRs). The triacs are downright useless for switching many types of loads, including small power supplies, small AC dosing dumps, and as you mentioned large inductive loads like chillers and magnetic ballasts (E-ballasts like for T5s have a soft start and are power-factor corrected so don't look inductive anymore).

 

[Bigtrout]

Good advice and summary.

Even the commercial units suffer from some of these problems. E.g., the APEX EB8 have two outlets on relays and 6 on triacs (internal SSRs). The triacs are downright useless for switching many types of loads, including small power supplies, small AC dosing dumps, and as you mentioned large inductive loads like chillers and magnetic ballasts (E-ballasts like for T5s have a soft start and are power-factor corrected so don't look inductive anymore).

Yes, to put these in an apex and expect the end user to be able to know what types of loads to use is a bit much. Even electrical engineers missed this in designs when PLCs first started using triac outputs.

And to trust an SSR with no datasheet available from china, no thanks.

While im not a fan of the Songle relays used in the ADJ power board and most of the 8 channel relays we use in our builds, the relays are UL listed, and have a datasheet available, they just lack the usable life of a better branded relay, so they work safely just not as long as better quality relays can when switching heavier loads. Then again an 8 channel board can be had for the price of one good relay and base, and are fine for alot of the small equiment used in the average aquarium.

In industrial machinery control panels with tons of relays in them, the vast majority are still electromechanical relays, with SSR relays used for very specific uses and in uses that have been designed by an engineer, and its even more rare to see an SSR deployed in the most important use of all, in safety circuits like emergency stop circuits, etc.

 

[theatrus]

Yes, to put these in an apex and expect the end user to be able to know what types of loads to use is a bit much. Even electrical engineers missed this in designs when PLCs first started using triac outputs.

And to trust an SSR with no datasheet available from china, no thanks.

While im not a fan of the Songle relays used in the ADJ power board and most of the 8 channel relays we use in our builds, the relays are UL listed, and have a datasheet available, they just lack the usable life of a better branded relay, so they work safely just not as long as better quality relays can when switching heavier loads. Then again an 8 channel board can be had for the price of one good relay and base, and are fine for alot of the small equiment used in the average aquarium.

In industrial machinery control panels with tons of relays in them, the vast majority are still electromechanical relays, with SSR relays used for very specific uses and in uses that have been designed by an engineer, and its even more rare to see an SSR deployed in the most important use of all, in safety circuits like emergency stop circuits, etc.

Those Songle/Ningbo relays are a treat in cheap. $0.20 in quantity and this is marketed for the US market (would be cheaper locally).

https://lcsc.com/product-detail/Relays_SRD-12VDC-SL-C_C30431.html The UL file number is real as well. (https://iq.ulprospector.com/en/profile?e=89469)

But I'd much rather buy an Omron relay for anything high power

 

[b4tn]

Very good info, thanks @Bigtrout . I was just getting ready to ask what about the commercial controllers that use SSR's but @theatrus nailed it. I am still in the planning stage of my power strip rebuild and think I will go back to the plan of mechanical relays for everything except for the heater which will be a zero cross 40 amp SSR.

I do have a couple questions regarding my concerns. My wavemakers are DC Gyres that sit on each side of the tank and alternate. Each wave maker is switched on 12 times and off 12 times in a 24 our period. I really wanted to put those on an SSR for extended life but will stick with mechanical. are there any pre made, opto isolated, boards for the high end relays?

I would really like to use PWM to control the Gyres but I really dont want to spend $250 for a pair of interface controllers and I am not smart enough to design my own. Any other ideas for switching them without a mechanical relay? Maybe a mosfet on the DC side? If I recall the power supply is 24 volt 3 amp.

 

[Bigtrout]

I think a power mosfet would be fine to pwm those...

Dont take my caution wrong, my warning was about indiscriminate use in AC applications with mains power being switched.

 

[Ranjib]

I think a power mosfet would be fine to pwm those...

Dont take my caution wrong, my warning was about indiscriminate use in AC applications with mains power being switched.

These power heads dont need BLDC/BEMF style drivers? I am very curious which one can work where. I use power mosfets in 12V single led strips only. I know meanwell drivers are popular for constant current usage (like LEDs) , but if I understand correctly we can use power Mosfets as well. I really want to know what the pros and cons of using these interchangeably. In terms of efficiency, safety, heating and convenience (sink/source types).

ps. I am very fortunate to have folks like you, @theatrus here in this thread to guide us through. Thank you again.

 

[b4tn]

@Ranjib you are correct they need BLDC drivers. Right now I just switch the control box on and off via the AC power supply. What I was talking about was using a mosfet on the DC power side of the controller to turn it on and off.

 

[Bigtrout]

@Ranjib you are correct they need BLDC drivers. Right now I just switch the control box on and off via the AC power supply. What I was talking about was using a mosfet on the DC power side of the controller to turn it on and off.

Seek and ye shall find...here is a bldc driver that works from 6 to 50 volts and uses a 0 to 5v pwm signal as input
https://www.amazon.com/gp/aw/d/B072JTB4R8/ref=ox_sc_act_image_1?smid=A2PMIWMSUTAYGS&psc=1

 

[bishoptf]

Seek and ye shall find...here is a bldc driver that works from 6 to 50 volts and uses a 0 to 5v pwm signal as input

Missing link? eh Nevermind