How to set VR1 + think up some correctness tests
Posted: Fri Dec 09, 2011 3:52 pm
This kit looks fantastic, thanks so much for making it. I'm a teacher, so the lens though which I see everything is "where are the students going to get stuck", and that leads to my questions....
1. It would be great to add a step in the instructions to spell out how to set VR1. Actually I imagine having a few different instructions, depending on how much the user cares and what hardware they have available. (Putting answers in the forums is great in the short term, but ultimately this should be spelled out in the actual instructions.)
a. you can just rotate VR1 to the middle of its range , and that will actually work fine (I don't know if this is true, I'm just guessing)
b. if you have a multimeter and want to set VR1 more closely, the procedure is (something)
c. (as above, but the user has access to a 1 GigaOhm resistor)
Also maybe document the relationship between VR1 and the SBM-20 voltage, and in turn the effect of the SBM-20 voltage -- does that increase or decrease the min event it can detect and how many events per second it can handle.
2. I would love the docs to have short list of correctness-measurements one could make on an assembled, powered off board that would check for common errors -- either swapping components around or bad solder joints. Imagine having a room full of kids putting these together, and when one raises their hand and calls out "hey it's not working" ... it's nice to have a clear list of checks to point them to, even if the checks only catch some errors. It's ok if the checks are labor intensive, or tedious, or require jumpers to short across some components or whatever. If the thing is not working, they don't have anything to do anyway, so give them something to do. (I'm happy to contribute a diagram or writing for this, but the electronics is not my area.)
Just thinking out loud here, but I wonder if there a check that could be implemented where the SBM-20 is replaced by some easy to get resistor, like say 1 MegaOhm, and then power the thing up and check the voltage .. would that work as a check on the HV side of things, or would that just instantly fry the whole thing? I'm guessing that the HV side is the most common source of problems, so I'd love for someone to come up with some sort of end-to-end functional check of that side.
Thanks!
Nick
1. It would be great to add a step in the instructions to spell out how to set VR1. Actually I imagine having a few different instructions, depending on how much the user cares and what hardware they have available. (Putting answers in the forums is great in the short term, but ultimately this should be spelled out in the actual instructions.)
a. you can just rotate VR1 to the middle of its range , and that will actually work fine (I don't know if this is true, I'm just guessing)
b. if you have a multimeter and want to set VR1 more closely, the procedure is (something)
c. (as above, but the user has access to a 1 GigaOhm resistor)
Also maybe document the relationship between VR1 and the SBM-20 voltage, and in turn the effect of the SBM-20 voltage -- does that increase or decrease the min event it can detect and how many events per second it can handle.
2. I would love the docs to have short list of correctness-measurements one could make on an assembled, powered off board that would check for common errors -- either swapping components around or bad solder joints. Imagine having a room full of kids putting these together, and when one raises their hand and calls out "hey it's not working" ... it's nice to have a clear list of checks to point them to, even if the checks only catch some errors. It's ok if the checks are labor intensive, or tedious, or require jumpers to short across some components or whatever. If the thing is not working, they don't have anything to do anyway, so give them something to do. (I'm happy to contribute a diagram or writing for this, but the electronics is not my area.)
Just thinking out loud here, but I wonder if there a check that could be implemented where the SBM-20 is replaced by some easy to get resistor, like say 1 MegaOhm, and then power the thing up and check the voltage .. would that work as a check on the HV side of things, or would that just instantly fry the whole thing? I'm guessing that the HV side is the most common source of problems, so I'd love for someone to come up with some sort of end-to-end functional check of that side.
Thanks!
Nick