No, it needs to be above 9v by a margin because this is a first approximation. The value of 2000uF gives 10% ripple, or 2.4v p-p so approx 9.6 to 14.4v at the full 500mA load. It might even be a bit on the small side.

Can I use multiple smaller sized caps instead of one huge one?

 

Given the reactive load, sizing a Triac and it's associated snubber network, is not something I'd recommend. And an SSR to meet this requirement is considerably more expensive than the relays. Plus triacs and ssr are not able to fully isolate the load from the supply. Stay with the relay, it's a simple and safe solution to the need.

CRYDOM company makes a very good and very well isolated line of industrial quality SSR devices rated for 240 volts mains power switching. The standard ones are rated for 20 amps load current, they also make higher rated ones. An added benefit is that there are models that trigger with 5 volts and 20 milliamps, so controlling them from logic is possible. They are both physically and mechanically quite rugged as well. And possibly less expensive than an equivalent magnetic relay of similar capability. There are also other brands of SSRs that have similar mounting arrangements and similar specifications, and they might be cheaper.

 

CRYDOM company makes a very good and very well isolated line of industrial quality SSR devices rated for 240 volts mains power switching. The standard ones are rated for 20 amps load current, they also make higher rated ones. An added benefit is that there are models that trigger with 5 volts and 20 milliamps, so controlling them from logic is possible. They are both physically and mechanically quite rugged as well. And possibly less expensive than an equivalent magnetic relay of similar capability. There are also other brands of SSRs that have similar mounting arrangements and similar specifications, and they might be cheaper.

The CRYDOM SSR are good, but not cheap. The EL240A20-5 (5v control, 240v/20A zero-crossing switch) is £25 give or take just about everywhere.

Granted you can get a no-brand one on eBay (not logic 5-32v, not zero-cross switching) for about £10, but I wouldn't trust it, certainly not in a safety circuit.

 

Found this from CELDUC (SSR manufacturer), which references IEC standard EN947, category AC-55a Switching of Discharge Tubes (at http://www.celduc-relais.cn/wp-content/notes_techniques/ac55a.pdf)

Their 35A relay SO843070 is also £25

 

Plus triacs and ssr are not able to fully isolate the load from the supply. Stay with the relay, it's a simple and safe solution to the

Not true. Like I said. I have done this.
The opto isolator driver isolates the load from the DC supply. I agree however that a relay is easier to implement.

 

Not true. Like I said. I have done this.
The opto isolator driver isolates the load from the DC supply. I agree however that a relay is easier to implement.

Certainly there are isolated drivers for SCRs and Triacs, and so isolation is available, BUT that is a bit more effort, complexity, and cost added to the project. On top of that, some ballast types really must have very close to the full sine wave or they do not function correctly. If they are not listed as "dimmable" then there could be incorrect operation. or failure. I have seen both.

 

Certainly there are isolated drivers for SCRs and Triacs, and so isolation is available, BUT that is a bit more effort, complexity, and cost added to the project. On top of that, some ballast types really must have very close to the full sine wave or they do not function correctly. If they are not listed as "dimmable" then there could be incorrect operation. or failure. I have seen both.

frankly...this is my last post on this thread. I wouldn’t “gift” anyone something that could potentially cause bodily harm, especially when not professionally engineered and certified..

good luck with your project..

 

Not true. Like I said. I have done this.
The opto isolator driver isolates the load from the DC supply. I agree however that a relay is easier to implement.

Certainly there are isolated drivers for SCRs and Triacs, and so isolation is available, BUT that is a bit more effort, complexity, and cost added to the project. On top of that, some ballast types really must have very close to the full sine wave or they do not function correctly. If they are not listed as "dimmable" then there could be incorrect operation. or failure. I have seen both.

You both misunderstood me; I wasn't talking about galvanic isolation driving the SSR, I was referring to the ability of an SSR to isolate the load from the supply in the case of a fault or maintenance.

Chapter 53 of BS7671 (the Regulations - they govern electrical installations in the UK) states in section 537.2 Isolation: Semiconductor devices may not be used for isolation.

Which is why I've been saying "relay" from the start.

 

Can I use multiple smaller sized caps instead of one huge one?

Yes, it would be common practice to do so, putting 3 or 4 in parallel. Eg layout for 1000uF 25v x 4, then on test see how many you actually need.

 

You both misunderstood me; I wasn't talking about galvanic isolation driving the SSR, I was referring to the ability of an SSR to isolate the load from the supply in the case of a fault or maintenance.

Chapter 53 of BS7671 (the Regulations - they govern electrical installations in the UK) states in section 537.2 Isolation: Semiconductor devices may not be used for isolation.

Which is why I've been saying "relay" from the start.

Certainly a relay will provide the desired isolation. BUT to do any kind of service the only smart move is to switch off and UNPLUG the device being serviced. Especially with gas discharge lamps of the tubulat type there is no way to change them with the power on that is not foolhardy. The ONLY safe way to work on those is with the power OFF.

 

Fully agree & not disputing that, but the point was that safety isolation can't be an SSR. So, if there's any form of automated isolation it has to be a relay.

 

Alright, Thanks. I am gonna stick with the relay. Have to start working on interfacing LCD with a standalone microcontroller, selecting the correct caps and PCB.

 

Fully agree & not disputing that, but the point was that safety isolation can't be an SSR. So, if there's any form of automated isolation it has to be a relay.

ON/OFF control of sections of an appliance does not require safety isolation within the package. At least not in my country. I am aware of places where totally enclosed, fully interlocked, electrical systems still require plastic shields inside. An adequate explanation has never been given as to why.

 

That's one of the fascinations on forums (fora?, forae?) like this... the multiplicity of 'right' answers

 

https://www.meanwell.com/Upload/PDF/IRM-15/IRM-15-SPEC.PDF

Would this be a better alternative than building the power supply(5v) myself?

 

https://www.meanwell.com/Upload/PDF/IRM-15/IRM-15-SPEC.PDF

Would this be a better alternative than building the power supply(5v) myself?

Yes, if it will give you the current you need.

http://cds.linear.com/docs/en/application-note/an73f.pdf
http://cds.linear.com/docs/en/application-note/an35f.pdf

Originally presented by Jim Williams:



Advice for those who "want" to build a SMPS.

 

The 12 volt supply in the link will certainly supply the 12 volt needs. and the 5 volt model will handle the processor load very well.

 

https://www.meanwell.com/Upload/PDF/IRM-15/IRM-15-SPEC.PDF

Would this be a better alternative than building the power supply(5v) myself?

Given the cost of two of that (1 for 5v, 1 for 12v) is < the component parts of your original plan, then yes, as suggested all along.

But you don't need a 15w, a 5v 3W (0.6A) and a 12v 5W (0.4A) is more than enough, and for under £12

Alternatively consider a dual output off-board PSU, though its physically larger, such as:
https://www.mouser.co.uk/ProductDetail/MEAN-WELL/RD-35A

 

Yes, if it will give you the current you need.

http://cds.linear.com/docs/en/application-note/an73f.pdf
http://cds.linear.com/docs/en/application-note/an35f.pdf

Originally presented by Jim Williams:

View attachment 212580

Advice for those who "want" to build a SMPS.

Thanks for the application notes. Will give it a read.

The 12 volt supply in the link will certainly supply the 12 volt needs. and the 5 volt model will handle the processor load very well.

Thanks.

Given the cost of two of that (1 for 5v, 1 for 12v) is < the component parts of your original plan, then yes, as suggested all along.

But you don't need a 15w, a 5v 3W (0.6A) and a 12v 5W (0.4A) is more than enough, and for under £12

Alternatively consider a dual output off-board PSU, though its physically larger, such as:
https://www.mouser.co.uk/ProductDetail/MEAN-WELL/RD-35A

Thank You. Yes, Im working on the BOM cost now.

 

Can I get X7R for all ceramic capacitors? And should both my fuses(mains, transformer secondary) be slow blow?