@ dobova I finally had a little time tonight to start trying to figure out how to integrate this part into my module. I’m not quite sure how this would work. How would the LED inside the opto be powered since X2-1 would be open and X2-2 would be ground? All this module does is monitor a break in ground.
@ ianlee74 - I’m sorry Ian, the schematic coudn’t be used “as is” you are right. The HCPL chip has a logic level output so that when optoled is on, then you have logical 0 (it has a NOT) on output.
The problem is that on the input side, to be really insulated, you need to manage a power supply separated from gadgeteer boards. This is a mess. If you want simply sense a GND break, may be this circuit is an expansive complication. I will look later to try to add your feature.
In the attached picture the modifications for GND loop. If you want to add LED you can choose to have on input side or gadgeteer side. VCCIO is an extra supply separated from gadgeteer rails and R5/R6 must be calculated accordingly.
@ dobova - Yea, that’s what I thought. Adding a separate power supply would be a bit much for this little module. 
@ ianlee74 - Ian what’s happened for this module, You definitely abandon it? It is interesting and useful …
@ dobova - sorry, I just pulled up this thread and saw that I never replied to you. I haven’t abandoned it. I did get tired of searching for parts and put it aside a bit in hopes that I’d turn up some good idea on how to solve this problem. I definitely don’t want to give any to anyone until I’m certain that I won’t be responsible for frying their mainboard.
This seems like it should be such a common problem that there would be an IC that handles both the low & high side protection but I haven’t found one yet. The VESD05A8A that I’m using for ESD protection should handle one side fine but I can’t seem to find just the reverse of it that I can use for the other side. I think a circuit like the attached will be sufficient for this module but I don’t want to place that many parts or my module is going to have to get even bigger. Do you know of a single chip solution that does this?
The circuit was taken from:
@ ianlee74 -
Interesting link, the doc on Digikey site is very good.
Really I haven’t better idea and normally I use BSN70 or BAT4x for protection. If I need really good separation I go optoinsulators.
The circuit you have implemented seems good and need minor changes due to the led problem.
Can you provide a link? I can’t find anything using those keywords that seems relevant.
I actually solved the LED problem by simply removing the LED_EN idea. The LEDs are always enabled now. If the user has a normally on situation and they want to save power by disabling the LEDs then they can simply remove them 
I’m sorry, the diodes are BAS20-7, (BSN are Mosfet), BAT42 or BAT43. You can find on Mouser.com
This are diodes, that implement what is described in the Digikey document, nothing sophisticated.
OK. BAT43 it is. I’m going to finish this thing up and get the new boards ordered this weekend. Thanks!
@ ianlee74 - take a look at bas20-7 it’s better and you have 1 component with 2 diodes
I looked at the BAS20-7 but I was concerned about it not being a Schottky. Will it be fast enough to trip before the internal diodes are reached?
Also, the two input version is more than double the cost of two BAT43s. I may have to play with the layout to decide which version to use.
@ dobova - Problems with Eagle kept me from finishing up this weekend but it turns out it was fate. Today I found the part I was wanting originally. Ideally, I’d have 4 or 8 pairs on a single chip but this will work fine 
http://www.digikey.com/product-detail/en/BAT54SDW-7-F/BAT54SDW-FDICT-ND/725056
@ dobova - I finished up the revisions and re-routed the board (again). There are now 49 parts on this little module. We’ll see how long it takes to assemble one in a week or so when they return from DFRobot. 
@ ianlee74 - Hi Ian, I missed your last reply on this thread … strange I didn’t get mail about new post … but this morning I get advise …
I took a look at the BAT54 and it’s ok, I think. They are 30V diodes but they are very fast (5ns).
Wonderful Ian … thank you for the information, this part is very interesting.
Hmm, I have been thinking about this little module. As you might have seen I am using lots of different sensors that are open or closed collector outputs, or relay on/off outputs.
And the noob question here is: Can this module be used with those simple sensors as well? I am dreaming of easier connect to 2-4 sensors…
Thanks, looks great!
Maybe… This module only detects whether there’s an open/closed circuit. So, if you need your Gadgeteer mainboard to power a sensor/relay then this module probably isn’t going to help you much. However, if you’re trying to detect if a remote relay/sensor is in a high/low state then this could possibly be a good solution if the output is within the voltage limits.
As long as you used a voltage divider to lower the 10V signal to <5V and connected the grounds then I think it would work fine. This isn’t a scenario I had ever considered but I don’t see why it wouldn’t work.
The v1.2 boards arrived and everything looks good so far except that I messed up the mask on the pads around the bottom of the holes for the spade connectors. There’s plenty of solder surface on top, so I’m not going to worry with ordering another batch unless some other bigger problems are discovered.
(no animals were hurt [much] in the making of this film)
@ dobova & @ njbuch - please send your mailing addresses to ian → houseoflees.net. I need some beta testers
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@ ianlee74 -
Oh waw Ian … Mouse Trap is absolutely a must !! I will use against my guys when trying to stole my preferrred chocolate !!! In this case not animal hurted, but some children will blown up from my 10W laser beam!
Beautiful board !
PS: You made it with hatched gnd plane ? Interesting …