Tag Archives: Geiger Counter

Particle Update

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I’ve been ignoring my Geiger counter for awhile now, but I picked it back up and made some progress again. For some reason, I just wasn’t getting the 555 based HV power supply to generate a high enough voltage. In frustration, I bypassed the 555 and fed a PWM signal in from a microcontroller board that I have laying around.

That fixed the problem. I still don’t know why I wasn’t able to the the 555 doing what it was supposed to do. I’ll have to spend some more time on that some other day, but for now, I’ve prototyped it out and I’m happily detecting particles. I whipped out the new layout and will send off to Sunstone.com for another set of PCBs.

I’ve also replaced the Atmel chip with a PIC. I don’t have anything against Atmel. I’m just more familiar with PICs. Once I’ve built a few of these, I’ll change to really small packages — QFNs or BGAs for the chips — to make the board a little more fitting with our assembly capabilities. The SOIC chips are fine, but our machines don’t even come close to breaking a sweat with things that big.

Duane Benson
We treat agoraphobia for PC boards

 

blog.screamingcircuits.com

ValueProto from Sunstone

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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.

DPAK in gieger 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 through-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 similar 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.

Duane Benson
Same bat-channel. Same bat-time. (Different real-time though)

blog.screamingcircuits.com