I think I'm done with the geiger counter layout. Now I just need to get the thing built up to see if it works. I'm pretty sure, but you never know. I have an idea... I'll build a prototype. And... I'll build it in as self-serving a way as I can. How might I build a prototype in a self-serving manner?
First, I'll use my company (and our partner Sunstone Circuits) to build it. Second, I'll write about it here. Technically, you're not really supposed to review your own stuff, but I really don't get to order things very often. I know all about Sunstones's PCB fab services, but I haven't used their ValueProto service so I'm using this as an opportunity to do so. This PCB looks like it should work for their "ValueProto" service as well as with Screaming Circuits' "SimpleProto" service. Small quantity, no leadless parts. Perfect for the simple and value services.
I actually made a small change since I last wrote about this design. The particular high-speed, high-voltage transistor in the original design isn't available in an SMT package. I could have still left that one part in thru-hole, but I didn't want to so I didn't. This is one of the reasons I understand the difficulties of parts substitution. I found two simialr parts. One in a SOT-23 and the other in a larger DPAK. I really wanted the smaller package, but the specs of the DPAK part were closer. The DPAK is quite a bit bigger than the SOT-23, but it fits.
When I pulled up the layout to take this screen capture, I notices that the "Q1" label was slightly on the big pad for the DPAK. That's not good. When I find a last minute error like that, I usually take that as a sign to go back and give everything another once-over. I'm going to do that tomorrow, so stay tuned.
Same bat-channel. Same bat-time. (Different real-time though)