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Wombat
12-01-2008, 11:36 PM
I have used the DCSSR's from Wjohn in a different way.

As My Display is Running off 24VDC and as I have no need to Isolate the Output Circuits from the controllers so to save a few Dollars I am running the display Unisolated.

Instead of using the Isolation I have bypassed the Opto Coupler using an NPN Transistor.
The Added Bonus is if you are not connected to a controller the outputs all turn on Full giving a Static Display.

The way that it works is when the output is off from the Renard the output is High. This turns on the Transistor and grounds the Gate of the Mosfet. (I am using 12V Gate Mosfets IRF540's Surplus)

When the output is enabled on the renard (Goes LOW) the transistor is turned off and the GATE goes high (12V) This turns on the output.
(This could be used with the same Mosfets as original design by using 78L05 Regulator)


http://www.doityourselfchristmas.com/forums/picture.php?albumid=34&pictureid=132

I have used the same boards for this I just have reassigned the holes in the board to suit the new design. This works well and no tracks have to be cut/modified.

I am testing this tonight on my display

P. Short
12-02-2008, 02:43 AM
So you just bend the leads of the transistors to fit in the opto-isolator holes, and connect the ground on the output side to the ground from the input side?

Wombat
12-02-2008, 09:39 PM
Here is the layout of the boards.

Note that Wjohn's boards are slightly different layout but similiar enough.

http://www.doityourselfchristmas.com/forums/picture.php?albumid=34&pictureid=136

Wombat
12-02-2008, 09:55 PM
Just a note to the circuit above.

Should you be running boards like the olsen which is an Open Collector output, you can add the 4 resistors (use 10k) for pull-ups next to where the OPTO-coupler was and short pins 1-2, 3-4, 5-6, 7-8 on the Opto-coupler holes. (outputs will no longer be on when disconnected)

Wombat

Wombat
12-02-2008, 10:02 PM
So you just bend the leads of the transistors to fit in the opto-isolator holes, and connect the ground on the output side to the ground from the input side?

Not quite right Phil. I am putting the Transistor into the holes for the resistors not the
Opto-isolator.

Matt_Edwards
12-08-2008, 06:34 PM
I do something similar.
Only I don't add the transistors. I simple hard wire from the R divider straight to the Microcontroller output. You need to invert the output logic. But hey that is why they call it software.

Matt

Matt_Edwards
12-08-2008, 06:54 PM
i should also mention that is you do this you need to ensure you have a good earth ? 0v connection between the controller and the SSR.

Cheers
Matt

Wombat
12-08-2008, 10:25 PM
Yes You can do it that way but I wanted to not have to change the firmware in all of the chips as I did not have a programmer on hand at the time. This would have prevented me from using the AC SSR's as well.

Also the IRF540 Mosfets that I had in stock have a Gate Drain turn on of >4V so I could be a little risky to drive them with the micro directly hence why I opted to use the transistors.

Yes you are also correct to say that you need a good GND from the controller as noise could turn on outputs randomly if you dont when you are driving the MOSFETS directly from the Micro.

Wombat

Matt_Edwards
12-08-2008, 11:05 PM
You are correct about the noise and drive, but as i keep the distance between the uC and the SSR short ( less than 600mm) I don't see it as an issue.

What distance do you have from the controller to the SSRs?

If I were driving a long distance I revert back the to optos.

the biggest hassle I have had is also the String voltage greater than 36v and you can't use a 7805 regulator. I ended up using a 7824 and a 7805 in my Icecles this year. This has to change to a better solution.

Matt

djulien
12-19-2008, 02:41 AM
As My Display is Running off 24VDC and as I have no need to Isolate the Output Circuits from the controllers so to save a few Dollars I am running the display Unisolated.

Is that a pretty hefty power supply, and did you build it or buy one?

don

djulien
01-01-2009, 02:59 PM
the biggest hassle I have had is also the String voltage greater than 36v and you can't use a 7805 regulator. I ended up using a 7824 and a 7805 in my Icecles this year. This has to change to a better solution.

Do you have a drawing or more details about that? I made some icicle mods for 2008, and I'm planning to make some more extensive mods for 2009, so I'd like to see more details of what you did.

don

Matt_Edwards
01-01-2009, 05:04 PM
Don,
this is what I did for my Icicles.
For my first year, everything went to plan - except the DMX USB adaptor.

the regulator is hopelessly inefficient, but I decided it didn't really matter as the LEDS are so Coooooool. And I just couldn't get a better solution with the time I had.

This year I will be designing some small SMPS that operate a 20-64Vdc in and good for 500ma load.

Cheers
Matt

budude
08-12-2009, 04:40 PM
I am playing with a layout using a PIC16F723 uC in a DC-Only configuration. Originally, I just plunked the controller bits (See http://doityourselfchristmas.com/forums/showthread.php?t=7193) and 4 x DCSSR bits on a single 4x8 board. Then I was asked (LabRat) on if the isolation was required and having just seen this post - that's a good question. Assuming I reverse the outputs of the PIC, can I drive the MOSFETs from the DCSSR portion directly and toss out the optos? I've seen other threads using BJTs instead of MOSFETs - so now I'm not sure which way to go... This would make the layout much easier to plan for sure! I'm hoping to stuff the board and it's associated PS in the same enclosure (CG1000/1500, etc).

Basically I am looking for a 16 channel DC controller to drive Frank's LED Strips. I know the existing coop controllers can do this but I'm attempting to create my own for the heck of it. I'm not sure I can run all 16 channels worth of power through the traces but I'll figure that out later.

Thanks
Brian

P. Short
08-13-2009, 12:21 AM
You might also think about using a pair of ULN2803 chips instead of MOSFETs if you don't really need the higher output currents that you can get with MOSFETs.

budude
08-13-2009, 03:22 AM
Hmm - yeah that might work. The data sheet claims up to 500mA continuous for each output. Does that mean that all 8 can be on at the same time (i.e. 4A total) - it doesn't clearly indicate that... If .5A isn't enough they can be doubled up I guess - this would still be cheaper than using the MOSFETs - and I'm thinking I won't need 19A any time soon!

Thanks for the tip Phil.

ErnieHorning
08-13-2009, 09:21 AM
Any one output can have up to 500 mA. Itís a percentage with more than one on at the same time. The far right shows maximum current per total outputs on at 100 % on.

http://img90.imageshack.us/img90/3664/uln2803aic.jpg

budude
08-13-2009, 10:48 AM
Ah - thanks Ernie (guess I should look at those little charts closer next time...) - so it looks to be ~175mA with all 8 on at 100%. If I doubled them up it would be 350mA or so which won't be enough either... Guess I'll stick with the MOSFETs for now - plenty of headroom anyway!