dc ssr dc troubleshooting

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daytimer

New member
I just got the latest rev 1.2 dc ssr boards from wjohn. I built one to spec but can't seem to get the mosfet to turn on. I have removed the voltage regulator and opto coupler, fed the board with 5vdc (using an atx power supply) and jumpered two of the pins on the opto socket to turn on one of the mosfets. Comparing the board to the data sheet for the mosfet, shouldn't the gate voltage be applied to pin 1? Looking at the board, it looks like the 5v gate voltage is being applied to pin 2 through the 470 ohm resistor with the 10k being used to bleed it off when turned off.
Without any pins being jumpered, the mosfet has 0v on the gate, 5v on the drain and 5v on the source. Jumpering a pin to "turn on" the mosfet yields the same results. I am using the FQPF13N06L MOSFET.
 
Check your 680ohm resistors . Sounds like the same problem I had last year and ended up being those I was supplied 680kohm instead of 680 ohm . Both read as .680 on my multimeter .680kohm and .680Mohm.
 
Well, I found that the traces on the board seem to be reversed. The trace off the opto goes to pin 2 on the mosfet and pin 1 on the mosfet is connected to the terminal block. The trace off the opto should go to pin 1 (gate) and pin 2 should be connected to the terminal block. I sent wjohn a pm to see what he thinks.....
 
daytimer said:
Well, I found that the traces on the board seem to be reversed. The trace off the opto goes to pin 2 on the mosfet and pin 1 on the mosfet is connected to the terminal block. The trace off the opto should go to pin 1 (gate) and pin 2 should be connected to the terminal block. I sent wjohn a pm to see what he thinks.....
Click to expand...

Soldered the componets to the correct side of the board have we ???
 
jmksparks said:
Soldered the componets to the correct side of the board have we ???
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yup. It wouldn't matter anyway.... The trace going from the opto to the mosfet goes to pin 2 of the mosfet. You can re-orient a 3 pin device any way you want and pin 2 will still be in the middle! So, the board feeds the voltage meant for the gate to the drain pin.
Attached is a pic of what I had to do to make it work. I cut the traces going to the 2 affected pins and rewired them according to the datasheet for the mosfet. The 1 port that is rewired works properly now.

dc ssr bottom.JPG
 
Wow, you're right -- looks like that board was set up for DGS pinout on the MOSFET (like the little TO92 ones) instead of GDS (left-to-right) like most power MOSFETs use. Anyone else using version 1.2 (a?) DCSSR boards?
 
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daytimer said:
This guy http://www.mouser.com/ProductDetail...GAEpiMZZMsrr1kXJis%2bJx8EKuMrsj0gqrY1DWE5a/Y= is a 7a DGS pinout. It should work for what I plan on doing.
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I think the Mouser catalog is a bit misleading on that one... it is rated for a max continuous current of 0.7A, 4.6A pulsed (with the duty cycle presumed low enough to not overheat it). Also, you need to swing the gate 10V for that kind of current (the chart looks like it'll do 2A peak with 5V of gate drive). Note that you'd also have to install it facing the opposite direction as the original design.

TN0604N3-G datasheet

Good luck!
Jon
 
The only thing the local radio shark had was some mps2222a's. They are max 600ma. My dc loads were going to be around 400ma max. That's cutting it awfully close, but I'll see how it plays.
I really wish I could find something heftier that would solder right in without any modifications.....
 
Unfortunately, that MPS2222A is a regular bipolar transistor instead of a MOSFET, though it might actually work for your purposes, if you're lucky on the gain of the transistor :closedeyes:

After some searching, I didn't turn up much in the way of power MOSFETs with SGD or DGS pinouts... here's one with SGD pinout that's 1.2 amps & 50 volts, 0.3 ohms Rds, that might work for you as long as your current stays below that:

VN3205 at Mouser

This is not going to be a generic solution for those of us that ordered DC SSR boards intending to draw several amps, though :eek:hmy:
 
daytimer said:
The only thing the local radio shark had was some mps2222a's. They are max 600ma. My dc loads were going to be around 400ma max. That's cutting it awfully close, but I'll see how it plays.
I really wish I could find something heftier that would solder right in without any modifications.....
Click to expand...

Just a heads up, the Ren48LSD uses the MPS2222's and has 48 400mA outputs.
 
dlovely said:
Just a heads up, the Ren48LSD uses the MPS2222's and has 48 400mA outputs.
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that's where I got the idea to try it. How are the earlier boards set up? With that part listed in the wiki bom, I can't imagine others haven't had this issue.
 
daytimer said:
that's where I got the idea to try it. How are the earlier boards set up? With that part listed in the wiki bom, I can't imagine others haven't had this issue.
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Did you ping John about it? If you look at the WiKi the pins chanded between versions. The new one on DIYLEDExpress matches the first version and what you had to modify this one to.
 
I did ping John about it. Other than cutting the traces, he doesn't have any other immediate solution. I asked him if he plans on updating the board to work with these mosfets.
I couldn't find the board wiring for previous versions, so I was wondering if it had somehow changed. I figured if it was this way on previous versions, somebody would have picked up on it.
 
dlovely said:
Did you ping John about it? If you look at the WiKi the pins chanded between versions. The new one on DIYLEDExpress matches the first version and what you had to modify this one to.
Click to expand...

Where in the WIKI are you seeing the pinout change? I've looked around (more than once), and all I found were the schematics. The symbol for the MOSFET changed a little bit, which leads me to think the new part may be mis-labelled in the library. (Just conjecture.. no direct proof). Are there pictures of the underside/layout anywhere?
 
LabRat said:
Where in the WIKI are you seeing the pinout change? I've looked around (more than once), and all I found were the schematics. The symbol for the MOSFET changed a little bit, which leads me to think the new part may be mis-labelled in the library. (Just conjecture.. no direct proof). Are there pictures of the underside/layout anywhere?
Click to expand...

Version 1.1 - Pin 15 from the Opto goes to bottom pin of the MOSFET

Version 1.2 - Pin 15 from the Opto goes to the center pin of the MOSFET

Maybe John had changed the BOM to use a new MOSFET and not updated the Mouser BOM to reflect his change to the design.

EDIT: This was my post 666. LOL
 
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Hmmm... I didn't consider those symbols as having pin markings. To me that simply showed connection to the GATE pin, which on the new library symbol, mapped to the wrong pin for the devices listed in the BOM.
 
LabRat said:
Hmmm... I didn't consider those symbols as having pin markings. To me that simply showed connection to the GATE pin, which on the new library symbol, mapped to the wrong pin for the devices listed in the BOM.
Click to expand...


I agree Andrew...I have emailed John for an explanation. I too see an issue here.
 
LabRat said:
Hmmm... I didn't consider those symbols as having pin markings. To me that simply showed connection to the GATE pin, which on the new library symbol, mapped to the wrong pin for the devices listed in the BOM.
Click to expand...

Yeah understood, but when you look at the PCB pictures posted in this thread you can see it goes to the center pin. If you look at the data sheet for the MOSFET the center pin is not the gate.
 
Understood. I'm all "eagle" based, so I don't know how all the other systems/software does it. If this error happened under Eagle, I would say almost certainly that there was a mis-alignment between the library symbol, and the library part. As the symbol in the schematic changed between 1.1 and 1.2, it is my conjecture that something similar happened here. I hope that either
a. Not too many PCB's were made or
b. A source for MOSFETS with the alternate pinout can be identified.

Modding a bunch of boards would be a pain.
 
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