Search found 13 matches

by wbp
Sun Mar 04, 2012 8:31 pm
Forum: Wifi Radio Project / Hacking the Asus WL-520gU
Topic: Spam on the forums
Replies: 4
Views: 46617

Re: Spam on the forums

Jeff,
I just started getting SPAM email sent to the email address I used to register here. It is a unique address, used ONLY to register on these forums.
William
by wbp
Thu Dec 15, 2011 12:12 pm
Forum: Geiger Counter
Topic: How to you measure the voltage
Replies: 15
Views: 10309

Re: How to you measure the voltage

I'm doing more testing but I really don't think the swapped resistors cause any problems. They might cause the HV supply to vary more with battery voltage, but on the flip side they make the circuit more tolerant of low battery voltages. I'm going to play with the circuit a bit more but since every...
by wbp
Thu Nov 24, 2011 4:56 pm
Forum: HV Rescue Shield
Topic: Rescue Shields temporarily out of stock
Replies: 4
Views: 6467

Re: Rescue Shields temporarily out of stock

Jeff, are these back in stock yet?
Thanks,
William
by wbp
Wed Nov 23, 2011 12:21 pm
Forum: Geiger Counter
Topic: Why the preference of the SBM-20?
Replies: 18
Views: 16275

Re: Why the preference of the SBM-20?

I picked up an Anton 6107 on fleaBay for around $52 with shipping. Modified the kit, reversing the terminals so it can poke out on the left side. Replaced the anode resistor with 1 M ohm, and the VR with a 20 ohm pot so I could get it up to 700 V. Seems to work quite well. With an AM241 source (from...
by wbp
Wed Nov 23, 2011 11:53 am
Forum: Geiger Counter
Topic: How to you measure the voltage
Replies: 15
Views: 10309

Re: How to you measure the voltage

If my calculations are right, for models 117 and 289 (the two that I have) the lowest range is 10.6 M and the others are 10 M ohm.

William
by wbp
Tue Nov 22, 2011 8:21 pm
Forum: Geiger Counter
Topic: Q: External power, 5v or 3v, current?
Replies: 3
Views: 3151

Re: Q: External power, 5v or 3v, current?

The Mega has a 3.3 V supply which is rated at 50 ma. If you don't have anything else using it, that's more than enough to run the geiger counter. Why not just use that?

William
by wbp
Sat Nov 19, 2011 3:34 pm
Forum: Geiger Counter
Topic: How to you measure the voltage
Replies: 15
Views: 10309

Re: How to you measure the voltage

Aha! Found this on Fluke's user forums: the HV probe manual states that: "* The input impedance of Autoranging Fluke handheld digital multimeters varies as a function of range. The only range that deviates significantly from 10 MW is the 3V (Models 21, 23, 25, 27, 70, 73, 75, 77) or 4V (Models ...
by wbp
Sat Nov 19, 2011 3:23 pm
Forum: Geiger Counter
Topic: How to you measure the voltage
Replies: 15
Views: 10309

Re: How to you measure the voltage

Interesting. Put both meters into manual range. On the lowest range, I get 4.0 V. On any of the higher ranges, I get 3.75 V. So there IS a change in input impedance in the lowest range, but if I do the math right, it's a 6% increase, not a decrease. Interesting that both meters exhibit the same beha...
by wbp
Sat Nov 19, 2011 2:40 pm
Forum: Geiger Counter
Topic: How to you measure the voltage
Replies: 15
Views: 10309

Re: How to you measure the voltage

I just went over it again. Checked Q1, Q2, D1, D2, L1, C3 is the smallest of the caps. Except for R5/R6 it looks just like the image on Flickr. I have two Fluke meters, a 117 and a 289. Specs for both give 10M Ohm input impedance for DC V. I will try putting the 289 in manual range and see if that m...
by wbp
Sat Nov 19, 2011 5:11 am
Forum: Geiger Counter
Topic: How to you measure the voltage
Replies: 15
Views: 10309

Re: How to you measure the voltage

Yes, fresh alkaline. Tried 2 different sets to be sure. Wouldn't low battery make the voltage lower? Original 15 ohm r8 measured right at 14.9.

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