DIS pin 7 and THR pin 6 need to be joined

I have them connected. I must have taken the screenshot before doing it

Three more checkpoints before I fully complete the schemactic and then I can start working on deciding the parts and PCB.
1) 555 timer for permanent MCU failure buzzer. (same logic with a higher timeout and NC config)
2) Standalone MCU instead of Arduino
3) LCD + touch buttons interface

Thanks everyone!

 

I suggested a 4-pole relay so that there would still be only one relay to drive, and separate contacts for each of the groups of lights.
Of course, I was not considering a PCB mounted relay, either. While relays are very reliable, they are also the most likely to fail part of the design, after 20,000 cycles or so. Tgat would take quite a while given that the package will probably not be used more than twice a day. Off-board mounting would make replacement simpler and allow easier use of an alternative part, if the original model is no longer available.

That's a valid point. Though moving to a 4P off-board relay doesn't greatly increase the range of options it seems. RS don't have much except a Schneider plug-in @ £17 and Digikey throws up a push-fit Panasonic 10A @ £25, Mouser a few Omron LY4 10A @£16, and they are all 12v coils.

 

"
Alright, Cool.
So separate PCBs for the power and logic. The power relays, transformer on one and the rest of the circuit in another.
Only one power relay, a 4-pole device. and it can attach to that board but not be soldered into it. The power transformer and the rest of the power supply can also be on that same board, which is often done on consumer electronics.
One comment about the cad software adding a connection for you: There is a convention existing that shows the one line as crossing over the other. That is because after a couple of copies the crossing forms a poorly done dot, looking like an intentional connection.

 

Beginner. Looking to get advice, suggestions and improvements for my circuit.

View attachment 211959

Thanks
Edit: Please do advice about safety and reliability of the circuit? What should be added/removed to make it more robust and reliable.

From an engineering standpoint, you need to know how much current you want out of your supply. Infinite isn't an answer. Figure out how much current you want out of the supply, and then instead of 12VDC to 5VDC through an LM7805 (it will get hot because you're dropping 7 unneeded volts across it), use something ahead to drop the voltage further to say 9VDC.

Or better yet, use a DC : DC buck converter... the ubiquitous MC34063A comes to mind.

 

"
Alright, Cool.
So separate PCBs for the power and logic. The power relays, transformer on one and the rest of the circuit in another.
Only one power relay, a 4-pole device. and it can attach to that board but not be soldered into it. The power transformer and the rest of the power supply can also be on that same board, which is often done on consumer electronics.
One comment about the cad software adding a connection for you: There is a convention existing that shows the one line as crossing over the other. That is because after a couple of copies the crossing forms a poorly done dot, looking like an intentional connection.

I am checking 4-pole relays they are very expensive. But I found a 20A inductive load rated relay for like $5.

https://www.te.com/commerce/Documen...trv&DocNm=T9G_1216&DocType=DS&DocLang=English

Please let me know if its good.

And the junction mistake was mentioned by @Irving, I connected the terminals following his circuit.

 

From an engineering standpoint, you need to know how much current you want out of your supply. Infinite isn't an answer. Figure out how much current you want out of the supply, and then instead of 12VDC to 5VDC through an LM7805 (it will get hot because you're dropping 7 unneeded volts across it), use something ahead to drop the voltage further to say 9VDC.

Or better yet, use a DC : DC buck converter... the ubiquitous MC34063A comes to mind.

I know my current requirements. Its around ~400mA. Have doubled it. So 1A is what I am looking at.
Btw, thanks for the chip. I will check it out.

 

You could use a DIN style 4 pole contactor, they come in 12dc to 230vac coil ratings.
See ebay 132531321576
Max.

 

From an engineering standpoint, you need to know how much current you want out of your supply. Infinite isn't an answer. Figure out how much current you want out of the supply, and then instead of 12VDC to 5VDC through an LM7805 (it will get hot because you're dropping 7 unneeded volts across it), use something ahead to drop the voltage further to say 9VDC.

Or better yet, use a DC : DC buck converter... the ubiquitous MC34063A comes to mind.

I checked out the datasheet. The datasheet maximum I(sw) is 1.5A, they recommend that I(sw) should be twice of desired output current. So does that mean I can only draw a maximum if 0.75A from it? And the switching accuracy is 2%, so that's about the same as LM7805.

 

I am checking 4-pole relays they are very expensive. But I found a 20A inductive load rated relay for like $5.

https://www.te.com/commerce/Documen...trv&DocNm=T9G_1216&DocType=DS&DocLang=English

Please let me know if its good.

And the junction mistake was mentioned by @Irving, I connected the terminals following his circuit.

Well, upside it will switch 20A into a standard ballast... but only rated for 6000 operations like that.

And, the show stopper, its only 1 pole, so not really useful.

 

OK, those are enclosed relays with push-on connections, and yes they are not cheap. They are also not the kind that I was thinking about at all. Those are, in addition to being enclosed, mechanically quite rugged devices. I will need to do some research to locate a current seller of the style of relays that I am talking about, usually called open-frame relays. They would be intended to mount inside electrical enclosures where unknowing folks would grab live conductors without any understanding about electricity.

 

Well, upside it will switch 20A into a standard ballast... but only rated for 6000 operations like that.

And, the show stopper, its only 1 pole, so not really useful.

Alright, Thanks! A single pole can still be used(if there is a noticeable savings in cost) if I am going to switch only live and a reliable relay is found right?

Edit: The RS has a 5v version G4W-2212P-US-TV5-HP-DC5 but the datasheet does not show a 5v version.

OK, those are enclosed relays with push-on connections, and yes they are not cheap. They are also not the kind that I was thinking about at all. Those are, in addition to being enclosed, mechanically quite rugged devices. I will need to do some research to locate a current seller of the style of relays that I am talking about, usually called open-frame relays. They would be intended to mount inside electrical enclosures where unknowing folks would grab live conductors without any understanding about electricity.

Thanks, I will search for them too.

 

Open frame relays aren't that common anymore, except for high-power RF switching. AFAIK none of the major manufacturers Omron, TE, Schneider, Teledyne, etc. offer them.

 

Open frame relays aren't that common anymore, except for high-power RF switching. AFAIK none of the major manufacturers Omron, TE, Schneider, Teledyne, etc. offer them.

I tried searching but I could not find any from the major distributors

 

I have used the open frame DP relays by P&B/Tyco such as the PRD versions.
Still available from various sources & distributors, or there is as I mentioned before, 4 pole DIN style contactors from many sources on the WWW.
Max.

 

BTW, when using relays such as the TE in your post #145, ensure you open the sealed vent 'pip' usually in the corner or halfway down one side.
Max.

 

I have used the open frame DP relays by P&B/Tyco such as the PRD versions.
Still available from various sources & distributors, or there is as I mentioned before, 4 pole DIN style contactors from many sources on the WWW.
Max.

Thanks. I will search for them.

BTW, when using relays such as the TE in your post #145, ensure you open the sealed vent 'pip' usually in the corner or halfway down one side.
Max.

Ok. May I know the reason for it?

I am selected two transformers. The datasheet does not have much info about the temperature ranges, etc. Wait for suggestion from you guys.

They are the same except one is rate 1.2A and the other 3.6A.

https://static6.arrow.com/aropdfconversion/bcba497af0dac8ac34acd82014a935468b6bfca5/fd5-10.pdf
https://static6.arrow.com/aropdfconversion/a34fca889483dc4ecf7c633e1856c3737fa1780b/fd6-10.pdf

Thanks

 

I have used the open frame DP relays by P&B/Tyco such as the PRD versions.
Still available from various sources & distributors, or there is as I mentioned before, 4 pole DIN style contactors from many sources on the WWW.
Max.

Although Max's suggestion didn't bear fruit, the PRD devices are £48, it did lead to this Omron surface mount relay. Its a DPST but importantly its contacts are rated for 300,000 operations switching 25A at PF0.4 and its only £10 at Mouser. That, IMHO, looks a good bet. But 12v 150mA coil only, you just can't get enough effort on a 5v coil for those chunky contacts. It keeps the AC wiring easy, with only 1 power cable to the UV box, or putting the relays in the UV box, only a LV control cable goes there.

So, go with a 12v supply (might need an up-rating for the heavier duty relay), use an efficient switcher to get down to 5v without heat and move all the AC off the board (inc mains transformer). Though to be honest, I'd just buy a 12v 2A wallplug supply off eBay for a tenner, less than just the cost of the transformer. Then you just need a simple 12v to 5v switcher, around £2 on eBay. It's just not worth making it...

edit - attached data sheet for Omron G7L-2A-TUBJ-CB-DC12 relay

 

Although Max's suggestion didn't bear fruit, the PRD devices are £48, it did lead to this Omron surface mount relay. Its a DPST but importantly its contacts are rated for 300,000 operations switching 25A at PF0.4 and its only £10 at Mouser. That, IMHO, looks a good bet. But 12v 150mA coil only, you just can't get enough effort on a 5v coil for those chunky contacts. It keeps the AC wiring easy, with only 1 power cable to the UV box, or putting the relays in the UV box, only a LV control cable goes there.

So, go with a 12v supply (might need an up-rating for the heavier duty relay), use an efficient switcher to get down to 5v without heat and move all the AC off the board (inc mains transformer). Though to be honest, I'd just buy a 12v 2A wallplug supply off eBay for a tenner, less than just the cost of the transformer. Then you just need a simple 12v to 5v switcher, around £2 on eBay. It's just not worth making it...

That's great. I can switch to 12v.

As suggested by @BobaMosfet I am looking at the MC34063A. I came across LMR33620 while doing so. They both accept a wide Vin. But I am not sure if they are as reliable as the 78xx's. Ti also has nice reference designs to start with.

https://www.ti.com/lit/ds/symlink/lmr33620.pdf?ts=1595001219323

Alright. I aiming not buy any off the shelf components for this project. I want to learn to build them.

The same transformers I linked to have a 12v version as well.
https://catalog.triadmagnetics.com/Asset/FD5-12.pdf
https://catalog.triadmagnetics.com/Asset/FD6-12.pdf

Thank You!

 

Ok. May I know the reason for it?

The PCT relays are usually sealed due to the flux removal process, if left closed, the interior can ionize with high current switching/arcing and cause contact damage.
The removable 'pips' allows the interior to clear..
Max.

 

The PCT relays are usually sealed due to the flux removal process, if left closed, the interior can ionize with high current switching/arcing and cause contact damage.
The removable 'pips' allows the interior to clear..
Max.

Thank You