I’m trying to figure out which transistors are used on the BOB-09118 Sparkfun Optoisolator breakout board so I can ensure they can handle the power I’m planning on using them to switch. Thank you.
On the product page, just below the price, you can select Documents
Here’s the spec sheet on the Opto Coupler:
It’s not listed on the schematic, but Q1 and Q2 are both MMBT2222A transistors.
Hope this helps, and have a great holiday weekend!
Folks,
I’m considering replacing a BOB-09118’s R5 and R6 to allow the board to supply more current to the devices I want to control.
Thanks to the earlier exchanges in this thread, I looked up the BOB’s output transistors. The can handle a few hundred milliAmps. I want to use them to supply roughly 20-25 mA at 5V.
To get 20-25 mA from the BOB, I’m planning to replace R5 and R6 with resistors in the 250 to 200 Ohm range.
So…
A) Do you foresee any problems arising if I make the substitution?
B) Can you tell me how to tell which of the BOB’s four 10K resistors are R5 and R6?
When I look at the top of the board (top = components are visible), and I put the optoisolator chip on the right, I see three 10K resistors across the top of the board, and one 10K resistor between the two transistors.
If we call the three across the top “TopLeft”, “TopMiddle”, and “TopRight”, and we call the one between the transistors, “MiddleLeft”, can you translate my names into the R3, R4, R5, R6 names used in the Board’s dwnloadable (PDF) Schematic?
Blake
Hi Blake.
What you’re going to need to do is download the [Eagle files for BOB-09118 and open those in Eagle CAD. That will allow you to match up the parts on the schematic with the positions they occupy on the board with the ‘Show objects’ tool in Eagle. (it looks like an eyeball)
You can download a free version of Eagle to view the Eagle files with in the link below.
](http://cdn.sparkfun.com/datasheets/BreakoutBoards/Optoisolator-v12.zip)
Thanks Chris,
But, unfortunately, I can’t just download a copy of Eagle. I looked into doing that before I posted my question yesterday. I’m doing this for a for-profit purpose, and using a trial version of Eagle/Fusion360 would create entanglements that I hope to avoid by posting my question here.
You appear to have a legal copy of Eagle … Can I convince you (or some kind soul) to use that “Show Objects” tool, and then post an edited version of your Capture2 JPEG (above) that would identify the the R5 and R6 resistors?
Blake
PS: A bonus would be for me to learn not only the locations of the R5 & R6 10K resistors, but for me to also learn the size (or part number) of that part, so that I can try to match the size (well enough) when ordering my replacement resistors.
You can download Kicad (it can be used in for-profit organizations) and import Eagle designs. Looking at the schematic above, R5 and R6 are most likely the resistor to the right of each transistor; a few seconds with a DMM would verify it. Make sure the resistors you chose have a high enough power rating.
This design is really intended for logic level signals, not for controlling power. I would either use it as a low-side switch (remove R5 and R6, and wire the negative or ground of the load to the collector of the transistor) or use it to drive a high-side switch.
/mike
n1ist /mike,
I understand. That’s why I’m not planning to use it to control “power”.
After the modification, I am using it to control a “high side switch” (IXYS CPC1779) . Like many devices, to turn on, that switch needs more than 0.5 mAmps (5 Volts /10,000 Ohms) flowing into its control input.
At high temperatures (60C) it needs as much as 20 mAmps in order to turn on.
Hence, my desire to supply 20 mAmps into that high-side switch.
Blake
TS-Brandon,
Thanks so much.
In my opinion, the image you posted would be a great addition to the documentation section of the BOB-09118’s “Documentation” web page …
Blake