| Solid State Relays (Not really GMC) [message #303557] |
Wed, 13 July 2016 22:53  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
I need a tutorial on Solid State Relays (SSRs) Specifically the DC-DC type. I have a solar application where the controller I will be using is turning on a 12 VDC to 120 VAC inverter for 10 minutes at a time. It will be used 3 or 4 times per night. The input to the inverter will be around 15 amps at 12 VDC from the battery(s).
At all other times the input to the inverter will be shut down to conserve battery storage capacity. The controller running all of this draws around 50ma at 12 VDC off of the same 12 VDC source. The controller will run 24x7. The controller can supply ground to the SSR at a maximum of 50 ma. These SSR's appear to draw less than 10ma.
I have never used SSR's before and I am reading that the trigger voltage (effectively the coil on a regular relay) can not be fed off of the same power source as the contacts that are being switched.
Also because power consumption is a major concern, I am trying to understand the amount of heat buildup and electrical power loss through the SSR's. It appears to be a lot since they are required to have a heat sink.
Someone please direct me where to go look for this type of information.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
|
|
| Re: [GMCnet] Solid State Relays (Not really GMC) [message #303559 is a reply to message #303557] |
Wed, 13 July 2016 23:43  |
Dave Mumert
Messages: 272
Registered: February 2004
Location: Olds, AB, Canada
Karma: 0
|
Senior Member |
|
|
Hi Ken
The input is optically isolated from the output, connecting them by using a common supply would circumvent the isolation. That
would be a bad thing IF you needed the isolation.
As you don't need the isolation and being that the input is optically connected to the output side of the SSR I don't see how using
a common supply would have any effect on the operation of the relay. Your controller may not like the voltage spikes that occur
when you disconnect the inverter but you should be able to deal with that, I suspect that is the reason for the recommendation to
use a separate power supply.
We used a lot of these in the score board controls, I don't recall ever having to use a separate power supply for the control side.
Digikey has lots of the Crydom hockey puck style units in stock. That is what we used, maybe other brands have different
requirements. You may need heatsinking.
Dave Mumert
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of Ken Burton
> Sent: Wednesday, July 13, 2016 9:54 PM
> To: gmclist@list.gmcnet.org
> Subject: [GMCnet] Solid State Relays (Not really GMC)
>
> I need a tutorial on Solid State Relays (SSRs) Specifically the DC-DC type. I have a solar application where the controller I
will be using
> is turning on a 12 VDC to 120 VAC inverter for 10 minutes at a time. It will be used 3 or 4 times per night. The input to the
inverter will
> be around
> 15 amps at 12 VDC from the battery(s).
>
> At all other times the input to the inverter will be shut down to conserve battery storage capacity. The controller running all
of this
> draws around 50ma at 12 VDC off of the same 12 VDC source. The controller will run 24x7. The controller can supply ground to the
SSR
> at a maximum of 50 ma.
> These SSR's appear to draw less than 10ma.
>
> I have never used SSR's before and I am reading that the trigger voltage (effectively the coil on a regular relay) can not be fed
off of
> the same
> power source as the contacts that are being switched.
>
> Also because power consumption is a major concern, I am trying to understand the amount of heat buildup and electrical power loss
> through the SSR's.
> It appears to be a lot since they are required to have a heat sink.
>
> Someone please direct me where to go look for this type of information.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #303560 is a reply to message #303558] |
Wed, 13 July 2016 23:51 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
I'll take a look.
I do not think it applies to what I'm doing which is radio control to about 200 watts of LED lighting. The radio control is not problem. It is supplying to power (120v) to the 51 LEDs that is the issue. There is no commercial power available so we are doing solar.
Thanks
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: [GMCnet] Solid State Relays (Not really GMC) [message #303561 is a reply to message #303559] |
Thu, 14 July 2016 00:01 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
Dave Mumert wrote on Wed, 13 July 2016 23:43Hi Ken
The input is optically isolated from the output, connecting them by using a common supply would circumvent the isolation. That
would be a bad thing IF you needed the isolation.
As you don't need the isolation and being that the input is optically connected to the output side of the SSR I don't see how using
a common supply would have any effect on the operation of the relay. Your controller may not like the voltage spikes that occur
when you disconnect the inverter but you should be able to deal with that, I suspect that is the reason for the recommendation to
use a separate power supply.
We used a lot of these in the score board controls, I don't recall ever having to use a separate power supply for the control side.
Digikey has lots of the Crydom hockey puck style units in stock. That is what we used, maybe other brands have different
requirements. You may need heatsinking.
Dave Mumert
Is the input always optically isolated from the output in these DC-DC SSRs?
I'll take a look at Digi-key and see what they have. Crydon is one of the brands that I have stumbled over so far. I am having trouble getting exact specifications on them and understanding how they work. Most of them are out of China and I do not read Chinese.
Thanks
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #303569 is a reply to message #303557] |
Thu, 14 July 2016 07:13 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
They work well on resistive loads - lighting, etc. If you're going to switch something reactive, I'd put a bucking diode across the switch and p'raps a small capacitor. They get hot because the switching element is a triac (essentially two SCRs wired back to back with a common trigger) and the junctions have a somewhat larger resistance than a pair of metal contacts. It isn't much - the spec sheet should show it - but it's there and will cause a bit of heat. I've used the high current ones for tower lights for years with good results.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
| Re: [GMCnet] Solid State Relays (Not really GMC) [message #303575 is a reply to message #303569] |
Thu, 14 July 2016 08:32 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
|
Senior Member |
|
|
Real SSRs will outlast any mechanical relay, there are special ones for inductive loads. Theyre not cheap, but they work.
We replaced 3 phase mercury contactors with SSRs and got a better MTBF, hard to believe a magnetic coil and a pool of mercury would ever fail, but they did, esp when cycling 100s of amps 10 times a minute, 24 hours a day.
Consumer grade SSRs are not nearly as reliable, but good ones with excess capacity should be fine.
As far as using the same power for both ends, yeah thats just for isolation. if the SSR is truly isolated how could it matter where the power came from ?
>
> They work well on resistive loads - lighting, etc. If you're going to switch something reactive, I'd put a bucking diode across the switch and p'raps
> a small capacitor. They get hot because the switching element is a triac (essentially two SCRs wired back to back with a common trigger) and the
> junctions have a somewhat larger resistance than a pair of metal contacts. It isn't much - the spec sheet should show it - but it's there and will
> cause a bit of heat. I've used the high current ones for tower lights for years with good results.
>
> --johnny
>
> --
> '76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
>
> "Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #303586 is a reply to message #303557] |
Thu, 14 July 2016 10:56 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
What if---/ you use the SSR to trigger an old school relay as the current carrying device? Best of both and less energy loss as heat as only triggering coil. Or am I missing something?
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #303607 is a reply to message #303586] |
Thu, 14 July 2016 17:17 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
I am thinking about going that way. (A relay and SSR combination)
I also found a relay that draws 35 ma. at 12 vdc on the coil and the contacts will handle 10 amps at 12 vdc. Unfortunately I need double the current on the relay contacts so using that relay will also require a second larger relay to handle the load.
The real problem here is the design of the controller. It was designed to control an external SSR. The controller has a 50 ma. (at 15 vdc) limit. The designer assumed that the user would be using an DC-AC SSR with 120 volts on the switched side. He sells a separate 120 VAC SSR add on to the controller to switch the actual load.
Our application (using solar) the load is 12 VDC and around 15 amps.
So the real requirement here is a DC SSR or relay that requires less than 50 ma. on the coil while switching say 20 amps at 12 VDC.
Johnny, would a DC SSR still be a triac? Or is it simply a single big SCR? I understand that DC and AC SSRs are different, but I do not know the differences.
Another thought is to stick a some kind of switching transistor between the controller and a 12 volt relay with about a 70 ohm coil. I do not know what to use there or quite how to design that circuit.
I might as well tell you what this project is. The project is to power 51 LED runway lights on approximately 8500 feet of cable. They installed the underground cable on one side of the runway a few weeks ago. This is the private airport site where we held the GMC Eastern states work rally a couple of months ago.
Going solar poses a whole host of problems including unattended outside installation of all of the equipment and weatherproofing everything. It will see occasional below zero and above 100 F. temperatures with varying amounts of sunlight from winter to summer.
Thanks for any suggestions you have. Commercial Power is not a viable option at this point.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #303617 is a reply to message #303557] |
Thu, 14 July 2016 21:31 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
I've never used an SSR for DC, dunno quite how they work. The problem you run into with an SCR is it will continue to conduct after it's triggeed until the current through it falls below the holding current - which is on the spec sheet. Not a problem with the triac because each time the polarity reverses, the conducting SCR ceases to conduct and appears as an open until it is triggered again. For DC, I'd use a high current switching transistor.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #303620 is a reply to message #303617] |
Thu, 14 July 2016 23:41 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
That is exactly what I was thinking. I found this tutorial and think I understand it now.
http://www.electronics-tutorials.ws/io/io_5.html
It appears that a DC-DC SSR includes all of the optical isolation and snubber circuits (arc suppression) that I need.
So I should be able to just order one that specs out to what I need on the input side (below 50ma at 12 vdc on what would be the relay coil side) and for what I need on the switch contact side.
I found some cheap DC-DC SSRs rated at below 50 ma. on the input side and 25 or 40 amps on the output or switched side.
Thanks Johnny for the input.
I hate learning new stuff at 72 years old.
I grew up in the vacuum tube era and remember the first transistor radio that I bought as a kid.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: [GMCnet] Solid State Relays (Not really GMC) [message #303623 is a reply to message #303620] |
Fri, 15 July 2016 08:33 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
|
Senior Member |
|
|
I would avoid mechanical relays if at all possible, a DC solid state relay is most likely a high voltage MOSFET with diode protection. They have very low turn on resistance and are very reliable.
I use MOSFETS to turn on inductive loads all the time and they basically never wear out whereas a relay is guaranteed to wear out.
Make sure your SSR has at least twice the rating of your MAXIMUM possible current.
>
> That is exactly what I was thinking. I found this tutorial and think I understand it now.
>
> http://www.electronics-tutorials.ws/io/io_5.html
>
> It appears that a DC-DC SSR includes all of the optical isolation and snubber circuits (arc suppression) that I need.
>
> So I should be able to just order one that specs out to what I need on the input side (below 50ma at 12 vdc on what would be the relay coil side) and
> for what I need on the switch contact side.
>
> I found some cheap DC-DC SSRs rated at below 50 ma. on the input side and 25 or 40 amps on the output or switched side.
>
> Thanks Johnny for the input.
>
> I hate learning new stuff at 72 years old.
> I grew up in the vacuum tube era and remember the first transistor radio that I bought as a kid.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #304179 is a reply to message #303620] |
Sun, 24 July 2016 22:52 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
Thanks to some off-net GMCers, I was able to find 2 appropriate DC - DC SSRs. One is Chinese and one USA made. I ordered both and the USA one (Crydon brand) is here now along with several other electrical components that I ordered.
I was directed to an on-line solar configuration tool by a GMCer. That was extremely helpful in determining actual solar requirements for this project. We determined that we need 85 watts of solar collector capacity and slightly more than 160 amp/hours (at 12 vdc) of battery storage. So we have two 83 watt solar panels on order. We will get the battery later.
The scope of this project keeps changing and the actual power that will be required also changes with it. It is not major changes but in the end the project could consume an additional 25%. So we are designing everything with lots of wiggle room for additional load growth.
Now I have other questions.
Inverters:
I am making the assumption that I do not need a true sine wave inverter to power an all 120 volt LED load. Modified sine wave should do. The all LED load is around 200 watts, so I have specified a 400 watt modified sine wave inverter.
The second Inverter question is starting the inverter under load. The inverter will only be powered for 10 minutes at a time about 4 times per night. Do I need to remove the load from the output when powering up an inverter and then apply the load after a 2 or 3 seconds delay?
I'm looking for comments on both of these.
Charge Controller
I have no problem sizing the charge controller but I am reading about PWM an MPPT controllers. I see some very expensive MPPT controllers and also very cheap ones out of China. Is an MPPT type charge controller worth the effort and applicable here?
Again I'm looking for opinions / comments.
I wish our friend Gan Gregg were still with us. I would be asking him these questions. I know others of you are doing solar in your coaches so I'm asking for your opinions and experiences.
Thanks
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #304187 is a reply to message #304179] |
Mon, 25 July 2016 01:06 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
|
Senior Member |
|
|
Can't comment about the other piece's but on the charge controller,I'd save your money and use a PWM controller. On a small array like yours you will be just as happy and so will your batteries.Mppt's have their places but with your low voltage panels you'd be wasting your money for no appreciable gain.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
|
|
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #304230 is a reply to message #304191] |
Mon, 25 July 2016 14:33 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
That is exactly what we are doing. The problem running low voltage lights is the loss over 4000+ feet of wire per circuit. We actually have 4 separate circuits of over 4000 feet each. Even using low power LEDs at 120 volts we still have 1/3 of the power lost in transmission losses. I thought of boosting the transmission voltage to 240 with a 120 volt neutral but the wire is already in the ground and it is 10-2 w/ground. Also I could not find readily available 220 volt LEDs in the base and size we need.
The LEDs have already been tested for best visibility and have been chosen based is those parameters. So 120 VAC it is.
Luckily since this is a private airport we can do whatever we want and the FAA has no say so in our decisions. All lighting will meet FAA standards when we are done.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #304270 is a reply to message #303557] |
Tue, 26 July 2016 12:28 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Get a sack full of high voltage transformeres - whatever's cheap on ebay. Run the 10-2 at 600 - 800V and knock it do0wn to 12 at the light. Loudspeaker xformers should work at the low current you're running per light and they're cheap n small.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #304297 is a reply to message #304270] |
Tue, 26 July 2016 18:12 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
What will that by me other than saving some line loss?
For transformers I would have to buy or make 70 weather proof enclosures for them. There is no room in the enclosures for transformers.
Also all of the LED lamps are 120 volt AC.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: Solid State Relays (Not really GMC) [message #304313 is a reply to message #303557] |
Wed, 27 July 2016 08:01 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Would merely save line loss. If there ain't room, it would cost more'n it's worth.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
