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Solid State Relay

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madcitysw

New Member
Hello, I am working on a 12V control board that will have a normal 30A relay, but the others one must be a fast switching that can handle switching serval times before stopping (so I think I need a solid state device that can handle i), they will be controlled by a 5V AVR chip. The Solid State device needs to able to handle at least 3A. The control board will be mounted in a car once completed. Can anyone help me with this...

Shane
 

Papabravo

Well-Known Member
I'm not sure what you are asking for help with. You seem to have your requirements nailed down. Are you asking for suggestions on components that might meet those requirements? If so the best thing to do is troll the manufacturers websites.

NEC makes relays
OMRON makes relays
check Digikey
check Mouser

All four places have selection guides that will help you make up your mind. The good thing about starting with online distributors is that you can get a pretty good idea of the part's availability.

The 30A Crydom Relays at Digikey look like they cost about $50.00. I guess you'd better unlimber your wallet.

There is nothing worse on this planet than finding the perfect part only to learn that it is not in stcok, has a 26 week lead time, and costs more than one mortgage payment.

Lately I've become enamoured with latching relays because they don't require continuous power dissipation after they've been pulled in or let go.
 
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mneary

New Member
Be careful when selecting solid state relays for 12VDC. Most SSRs require AC loads or they will never release.
 

slosjo

New Member
Why do you think you need a SSR? Mechanical relays can be very fast and reliable. They won't last as long as a SSR, but are much less expensive.
 

zevon8

New Member
I second the Mosfet idea. Maye a logic level FET, should do the job, especially given only a 3 amp load. Solid state relays are great for ugly inductive/capacitive loads or unpridictable loads. Or when you need 20 years service. Comes at a cost though, as noted above.
 

madcitysw

New Member
Well I really would also use a Mosfet, but I don't think I really know how to use it

I was thinking about a dual P-Channel Mosfet that is in a SO-8 package such as the STS4DPF30L

I not even sure if that handles low logic or not.
 

carmusic

New Member
i used those intelligent mosfet that are currently use in automotive industry :
http://www.st.com/stonline/products/literature/ds/7370/VN820.pdf
i have about 500 units that i sold without any problem, i drive windshield water pump with them.
Of course there a a lot of different model , just search for intelligent mosfet switch, they are fully protected for short-circuit and overtemp
i wouldnt use just mosfet in a car since if they fail they can become very hot and causes fire
 

ericgibbs

Well-Known Member
Most Helpful Member
madcitysw said:
Well I really would also use a Mosfet, but I don't think I really know how to use it

I was thinking about a dual P-Channel Mosfet that is in a SO-8 package such as the STS4DPF30L

I not even sure if that handles low logic or not.
What about these devices.? VN05's, logic compatable.

http://www.datasheet4u.com/share_search.php?sWord=VN05

EDIT: posted extract from datasheet.
 
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madcitysw

New Member
OK guys, I guess I be trying to use the High Side Smart Power SSRs. The only things I worry about right now it getting it to work because if I use the VN05Ns, that means I going to need at least 15 of these on a board, but if I use the VND05B which are the dual channels version, i only need about 8 of those. I not 100% sure how to understand the datasheet, but I was told in the past that the higher the RDS(on), the more power it needs to run. Since these relays will be drawing at least 3 amps each, but they are rated for more. Can anyone give me a idea what I should be doing. Are there any schematics that someone used these devices before?
 

ericgibbs

Well-Known Member
Most Helpful Member
madcitysw said:
OK guys, I guess I be trying to use the High Side Smart Power SSRs. The only things I worry about right now it getting it to work because if I use the VN05Ns, that means I going to need at least 15 of these on a board, but if I use the VND05B which are the dual channels version, i only need about 8 of those. I not 100% sure how to understand the datasheet, but I was told in the past that the higher the RDS(on), the more power it needs to run. Since these relays will be drawing at least 3 amps each, but they are rated for more. Can anyone give me a idea what I should be doing. Are there any schematics that someone used these devices before?
hi,
Why do you need so many, they are rated at 12A continous.?
Also they are TTL compatable.

Do you have a diagram to post for this application.?

What does this mean:
Since these relays will be drawing at least 3 amps each, but they are rated for more
 
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madcitysw

New Member
Yes, each SSRs controls different things. These are going to be used to controlled different types of EMRGERNCY LIGHTING like the ones are used for police and etc. I making my own for my needs and how I would like it. For Ex: I have the CPS690 series http://www.electro-tech-online.com/custompdfs/2008/04/13583.pdf, as you can see there are two wires to control which head to come on, one to change the pattern and the 30 amp relay will be used to power the devices, but the SSRs are used to control them. I using an avr atmega 128 to control the relays and it will also have another board that has the status leds and flat touch buttons on them. There also other lighting system in the car right now beside the whelen. There will be the following switches (Unlock/Lock, Main Power, Control1, Control2, Control3, Control4, Control5), it just depends on how you push the buttons in order to control the SSRs. I have not really started a diagram, but I already written a code that works great for the AVR in C.

ericgibbs said:
hi,
Why do you need so many, they are rated at 12A continous.?
Also they are TTL compatable.

Do you have a diagram to post for this application.?

What does this mean:
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,

The select switches are fused with a 3A fuse, so the VN05 will handle that OK.

The unit power fuse is 15A and according to the spec sheet rated at 9A.

The spec sheet shows the VN05 is rated at 12A continous.
 

madcitysw

New Member
Yes, that is true, but the 15A fuse is connected to the Red wire if you look again, the red wire is going to be connected to the 30A relay (which is the main power), but it uses the other two wire (blue & green) which are going to be connected to the SSRs, which draws very low amps. That is what controls the device to turn on or off. See what I coming from?

PS: Where can I order some of these VN05 since I can't seem to find a place online. I have already requested some explames
 
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ericgibbs

Well-Known Member
Most Helpful Member
madcitysw said:
Yes, that is true, but the 15A fuse is connected to the Red wire if you look again, the red wire is going to be connected to the 30A relay (which is the main power), but it uses the other two wire (blue & green) which are going to be connected to the SSRs, which draws very low amps. That is what controls the device to turn on or off. See what I coming from?
A simple block diagram would be helpful.

PS: Where can I order some of these VN05 since I can't seem to find a place online. I have already requested some explames
hi,
I will do a search, some suppliers are reporting its a 'discontinued component'
Let you know how it goes.
 

ericgibbs

Well-Known Member
Most Helpful Member
madcitysw said:
Hello, I am working on a 12V control board that will have a normal 30A relay, but the others one must be a fast switching that can handle switching serval times before stopping (so I think I need a solid state device that can handle i), they will be controlled by a 5V AVR chip. The Solid State device needs to able to handle at least 3A. The control board will be mounted in a car once completed. Can anyone help me with this...

Shane
Hi Shane,
Jumped back to your OP.
What switching speeds/rates are you expecting on the project.?
If the VN05 are too pricey, relays may be the second option.:)
 

madcitysw

New Member
Well like the whelen, it needs to be less than a second, maybe 500ms or something like that to change the pattern. It would destroy a normal relay, so that why I need something that is solid state. I was hoping that I could find something with very low RDS like the VN820 (40m ohms), but I don't think it handles TTL signals. Ain't 40m ohms lower than 0.18 ohms correct? I want to try and keep them cooled as much as possible. I was hoping to find dual or quad types, but their RDS seems high.

ericgibbs said:
Hi Shane,
Jumped back to your OP.
What switching speeds/rates are you expecting on the project.?
If the VN05 are too pricey, relays may be the second option.:)
 

ericgibbs

Well-Known Member
Most Helpful Member
madcitysw said:
Well like the whelen, it needs to be less than a second, maybe 500ms or something like that to change the pattern. It would destroy a normal relay, so that why I need something that is solid state. I was hoping that I could find something with very low RDS like the VN820 (40m ohms), but I don't think it handles TTL signals. Ain't 40m ohms lower than 0.18 ohms correct? I want to try and keep them cooled as much as possible. I was hoping to find dual or quad types, but their RDS seems high.
40milli:eek:hm: = 0.040:eek:hm: ..... 0.18:eek:hm: = 180milli:eek:hm:

You can level shift the MCU drive signals by using an intermediate BJT transistor or small FET.
 

madcitysw

New Member
OK, i got the samples today and noticed that the dual channel version has about 20 ohms extra than the signal one. I thinking about using the dual channel instead of the single, so my question is that the dual channel draws 200m ohms, how much watt and amp is that? Is there any extra protection that I should addd to them?

PS: Do I need a heatsink if I going to run these dual channel version to 6A for both channel? Which one do I need?
 
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