{"id":8116,"date":"2013-07-26T12:36:28","date_gmt":"2013-07-26T19:36:28","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=8116"},"modified":"2013-11-08T20:24:40","modified_gmt":"2013-11-09T04:24:40","slug":"2013-07-26-joule-thief-e-field-detector-contd","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=8116","title":{"rendered":"2013-07-26 Joule Thief E Field Detector Cont’d"},"content":{"rendered":"

\"DSC_0434S4\"<\/a>This is a continuation of my previous blog<\/strong><\/a>.\u00a0 I drew up a circuit (see the photo) and then built it, and I’ve been experimenting with it a little, and have some encouraging results.\u00a0 Time for another blog.<\/p>\n

As can be seen, the blue LED is glowing dimly.\u00a0 I originally used an alligator clip for the antenna but its surface area was larger and caused the LED to light much brighter, which made it more difficult to tell if the E field was changing.\u00a0 I soldered the short wire on and it was much dimmer, enough to tell that the circuit was working but not enough to confuse things.<\/p>\n

The circuit calmed down, but seemed erratic when I walked around with it on the clipboard.\u00a0 I took a single step, and the LED lit brightly.\u00a0 I raised my foot up and the LED lit brightly.\u00a0 It was so sensitive that it was detecting the change in the electric field in my body when I was walking on the wood floor.\u00a0 Dang, that’s sensitive!<\/p>\n

If I put the antenna close to electrical wiring, the LED lights up brightly.\u00a0 If I walk across the tile floor the LED lights up but not as bright as the wood floor.\u00a0 That seems logical, since the tile is more conductive and should build up less charge on the soles of my shoes.\u00a0 It used to be that one of these would really light up if it was brought near the face of a CRT monitor or TV, but I don’t have any CRTs, everything I have is a flat panel display.<\/p>\n

If I rub the armrest of a chair to build up a charge, the LED dims when I bring it closer, and gets brighter when I move it away.\u00a0 I’m thinking that means the charge is negative, and moving it away reduces the negative or increases the positive current in the base of the SS9014.\u00a0 When I hold the circuit, with my finger on the battery negative, and I rub the armrest and move my hand toward it and away from it, the LED gets brighter and dimmer.\u00a0 I rub a plastic water bottle across my pantleg and then bring it near (an inch or two) the antenna and the LED gets dimmer when it approaches and lights up brightly when it moves away.\u00a0 The weather has been more humid than usual, yet the circuit is still very sensitive.\u00a0 My guess is that when the humidity gets lower, it will be even more sensitive.<\/p>\n

The Evening News announced that the record for\u00a0 rainfall for July here in So Cal was broken – we had 0.09 inches.\u00a0 Big deal!\u00a0 Today was overcast all morning and finally cleared up late this afternoon.\u00a0 No rain today, but it rained earlier this week.\u00a0 The humidity is still above normal.<\/p>\n

More About The Circuit<\/h3>\n

I built the circuit on a piece of cardboard, and I’ve used cardboard previously, and found that it absorbs some moisture and becomes slightly conductive.\u00a0 In this case, the cardboard is from the back of a package and it is glossy on both sides, probably with glossy ink.\u00a0 I think that makes it less absorbent and it isn’t as conductive as plain paper.<\/p>\n

I used the SS9014D, which is a very high current gain NPN transistor, about 600 or more.\u00a0 The BC560C is also very high gain, so the amount of current gain from the input of the first transistor to the output of the second transistor is probably hundreds of thousands.\u00a0 If a 2N3904 and 2N3906 are used instead, the circuit should work, but it won’t be as sensitive, I believe.\u00a0 My circuit takes less than a milliamp at the 1k and coil winding, so if I divide that by 360 thousand, I get 2.5 thousandths of a microamp or 2.5 nanoamps.\u00a0 A microamp is a very small amount of current and this is much less than that – 1\/400th of a microamp.<\/p>\n

Another important point to remember is that the transistors are current operated devices.\u00a0 The antenna must cause a flow of current in the base to emitter junction in order to get a flow of current through the emitter\u00a0 to the collector.\u00a0 This is in contrast to the FETs such as the 2N7000, which has a gate that is sensitive to voltage.\u00a0 Thus if you move the antenna on this circuit, it will change the E field, and that change causes a current to flow to or from the base – the LED lights or dims.\u00a0 But once the movement stops, the E field stops changing and the current stops – the LED stops changing.\u00a0 With the 2N7000 MOSFET, the antenna would cause an electric field to build up on the gate (it’s a field effect transistor), and the 2N7000 would turn on and the LED would light up and stay lit, until the field changes<\/p>\n

The ANTENNA<\/h3>\n

I used a short 2 inch (50mm) piece of 24 AWG (0.5mm) solid insulated wire.\u00a0 It tends to get bent a bit, so a stiffer wire would probably be better.\u00a0 I originally used an alligator clip temporarily, but the circuit was too sensitive and it caused the LED to stay on most of the time.\u00a0 When I changed to the 2 inch wire, the LED stayed off most of the time and the circuit was a bit less sensitive.\u00a0 If you use a piece of heavier wire, or paper clip, it may cause the circuit to be more sensitive.\u00a0 If it does, just cut off a bit of it and retry it, and if it helps, you’re good to go.\u00a0 If not, then you may want to make it a bit shorter. If you cut off too much, just put a new one on or solder an extension on, or make it a T shape.\u00a0 You can tell people that the crooked design of the antenna is what makes the circuit work.\u00a0 “It’s like a water witching rod.\u00a0 The tree branch has to be just so.”\u00a0 Heh-heh!\u00a0 Read about that here<\/strong><\/a>.<\/p>\n

Also, if you use lower gain transistors such as the 2N3904 and 2N3906, then the circuit may be more sensitive with a longer wire.\u00a0 You’ll just have to experiment with it to see what’s the optimum length.<\/p>\n

I think that if the antenna wire has insulation, it will be more sensitive. The antenna wire picks up the electric field using its capacitance to the surrounding air, and if insulation is added, the plastic has higher dielectric constant than air, so it may increase the capacitance, which in effect should increase the sensitivity.\u00a0 In any case, you can compensate by changing the length of the wire.<\/p>\n","protected":false},"excerpt":{"rendered":"

This is a continuation of my previous blog.\u00a0 I drew up a circuit (see the photo) and then built it, and I’ve been experimenting with it a little, and have some encouraging results.\u00a0 Time for another blog. As can be seen, the blue LED is glowing dimly.\u00a0 I originally used an alligator clip for the <\/p>\n

(Read More…)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,17],"tags":[],"class_list":["post-8116","post","type-post","status-publish","format-standard","hentry","category-joule-thief-smps-dc-dc","category-meters-and-test-equipment"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/8116","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8116"}],"version-history":[{"count":16,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/8116\/revisions"}],"predecessor-version":[{"id":8788,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/8116\/revisions\/8788"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8116"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8116"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8116"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}