36v DC and SSRs

**mutleyrover** · 02-05-2015, 05:02 PM

I have got a variety of LED strings that all have wall warts which supply different voltages to the lights, some being AC and some being DC. This is what they supply:

24v AC

24v DC
25v DC
30v DC
31v DC
36v DC

I plan to use Renard controllers (plus 32, 64XC) with separate SSRs and group my lights together so that the 4 outputs from any one SSR will be the same voltage, that way I can use a single power supply in to the SSR to run all 4 sets of lights.

I therefore need some AC SSRs and some DC SSRs. As far as I can see the DC SSRs all seem to say that they can be used from about 6v to 30v DC. I'm therefore wondering if I can run my lights that require 36v DC. Is that too much power to put through the SSRs or will the boards stand up to 36v DC?

**efreeman1980** · 02-05-2015, 05:42 PM

Maybe a few of these would help?
http://www.ebay.com/itm/DC-DC-4A-4-5...item2a429a43ed

**P. Short** · 02-05-2015, 08:25 PM

There are two considerations here that I can think of. First, the transistors on the SSRs must be rated for higher than 36V if you are going to use a 36V power supply. I'd recommend using transistors (MOSFETs, most likely) that are rated for 60V or higher.

Some of the DC SSRs that are described here or in the wiki use DC regulators to drop the input DC voltage of the SSR down to a much lower voltage used for the optos and the gates/bases of the transistors. These regulators also need to be rated for much higher than 36V. Regulators that would withstand this higher voltage are much less common the regulators rated for 36V or lower, so it would take some research to find them.

**Matt_Edwards** · 02-06-2015, 02:43 AM

Ok the occasion where I needed to run some dc SSRs at 36v, I cut the track between the input voltage terminal and the volt regulator and then inserted a string of 6xSMD diodes.
Another option is to insert a 7824 regulator, but that more complicated.

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**mutleyrover** · 02-06-2015, 04:22 PM

Originally Posted by P. Short

There are two considerations here that I can think of. First, the transistors on the SSRs must be rated for higher than 36V if you are going to use a 36V power supply. I'd recommend using transistors (MOSFETs, most likely) that are rated for 60V or higher.

Some of the DC SSRs that are described here or in the wiki use DC regulators to drop the input DC voltage of the SSR down to a much lower voltage used for the optos and the gates/bases of the transistors. These regulators also need to be rated for much higher than 36V. Regulators that would withstand this higher voltage are much less common the regulators rated for 36V or lower, so it would take some research to find them.

The SSRs that I was planning to use were the Renard Plus DC SSRs. On the Renard Plus website it says about them being suitable for between 6v and 30v. However, since I posted this I noticed that they've been added back on to Radiant Holidays website with the following description:

The Renard Plus DC SSRhc is a Solid State Relay with 4 independent DC output Channels. The input for the control power is a +5VDC via the RJ45 connector. Each channel is then controlled by sinking this control power for each of the Optoisolators for a given channel. The optoisolators then in turn fire the channel MOFET. The MOSFETS are good for up to 60V and a maximum of 4A each. The total board power is limited to 10A.

From that description, and that being a kit including the BOM, I assume that I would be good to go with running my 36v DC lights with 36v DC power going through the SSRs, supplied by a SMPS.

**mutleyrover** · 02-06-2015, 11:39 PM

Originally Posted by P. Short

Some of the DC SSRs that are described here or in the wiki use DC regulators to drop the input DC voltage of the SSR down to a much lower voltage used for the optos and the gates/bases of the transistors.

I was just thinking about this comment. If I use an SMPS to supply the input voltage (in this case 36v DC), will the output voltage for the lights still be 36v? Is it the case that any regulators will drop the voltage for the optos, but not affect the voltage going through the board and out to the lights?

I'm not an electrician so my knowledge is limited, but I'm trying to learn!!

**P. Short** · 02-07-2015, 12:20 PM

Originally Posted by mutleyrover

I was just thinking about this comment. If I use an SMPS to supply the input voltage (in this case 36v DC), will the output voltage for the lights still be 36v? Is it the case that any regulators will drop the voltage for the optos, but not affect the voltage going through the board and out to the lights?

I'm not an electrician so my knowledge is limited, but I'm trying to learn!!

Yes, for those DC SSRs that have an on-board regulator. It appears that you don't have to worry about this for the SSRs that you mention in post #5 above, based on what you wrote in post #5 (since I have no direct knowledge of those DC SSRs).

**mutleyrover** · 02-07-2015, 11:55 PM

Originally Posted by P. Short

Yes, for those DC SSRs that have an on-board regulator. It appears that you don't have to worry about this for the SSRs that you mention in post #5 above, based on what you wrote in post #5 (since I have no direct knowledge of those DC SSRs).

Thanks Phil. Looks like they are probably the ones for me to go for. Just need to put an order in now!

**Matt_Edwards** · 02-08-2015, 04:46 AM

Are you intending to use these ones:
http://www.renard-plus.com/dcssrhc.html
I would suggest you investigate further with the designer as I suspect they won't work at 36 volts. The 7805 regulator is not rated to operate at 36v.

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**mutleyrover** · 02-08-2015, 08:37 AM

Originally Posted by Matt_Edwards

Are you intending to use these ones:
http://www.renard-plus.com/dcssrhc.html
I would suggest you investigate further with the designer as I suspect they won't work at 36 volts. The 7805 regulator is not rated to operate at 36v.

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Yep! They're the ones!! Maybe I'll see what they think...