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goldpic

A

Anonymous

Guest
Hey, Has anyone finished the goldpic project? I made the 4x14 inch mono coil and tried it out. It does work ok, but it is not much difference from the 7.5 inch coil which the kit calls for to make. Is there any different approaches to make the goldpic more able to reject iron better? I have tried 7.5x7.5 inch DD coil and didn't see really much improvements. Thanks Rick S
 
Hi Rick,
Got all the parts but haven't had time to finish it yet. Aquastars keeping me busy <IMG SRC="/forums/images/smile.gif" BORDER=0 ALT=":)">
The DD coil should give an improvement when used on iron mineralised soil but, as you say, there is not much noticeable difference on iron objects.
Eric.
 
Yesterday,I finish the Goldpic:
140 Ma to catch a coke can at 50cm and 42cm when you reset with a substitute of mineralised ground(ground effect)like a STANDARD RED HOUSE BRICK.
Mesured frecuency to Gate the 740 : 244Hz.
Good to experimemt with pic's design ,need better performance to justify the display and pic.
Thank you Trevor for this easy Kit and fun.....
Alexis.
 
Alexis,
An interesting post - I didn't think the frequency would be so low. Have you any idea of the receiver sampling delay?
g
 
I'm curious of a couple things as well. Why is the output of the front end op amp going through a 4066 instead of straight to the A/D convertor. Also, what is the time for A/D conversion because that would be the shortest possible sample delay due to limitations of the speed of A/D conversion. I am not familiar with the ADC0831 so I don't know what the conversion time is but an outboard convertor is necessary since the 16F84 doesn't have a built in A/D. I am building one using the 16F877 which does have a built in A/D. The minimum time is something like 20 to 25uS so its a little slow but since I am looking to build a boat tow unit, that will be plenty fast, just not for a coin/ring detector. When I do decide to build a coin detector, I will probably do the sampling and integration the old fashioned way and then read the result with the A/D so I can be sure of getting the 10uS to 15uS sample delay desired.
See ya,
Fred
 
Hi,
It appears that the signal coming from the front end is switched via a 4066. According to my scope its running around 220pps and the sample time is 32uS after the xmit pulse is shutoff. The sample period is 50uS. From there it appears to go to a sample and hold and then to the A/D. If I've made any mistakes on my measurements I appologize.
Thanks,
Charles
 
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