Unusual functions of cheap parts
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From: Murray on 26 Nov 2005 06:19 Frithiof Andreas Jensen wrote: > "Henry Kiefer" <otc_friend(a)gmx.net> skrev i en meddelelse > news:4385b3b1$1$27887$9b4e6d93(a)newsread4.arcor-online.net... > > >>Do you know of other interesting devices or circuits good for misuse? > > > Unbuffered logic gates can make a really bad but still useful analogue > amplifier by adding feedback and bias. > > E.G the CMOS 4007. See the old handbooks for a '100dB amplifier' based on a RCA chip - there was a wiring error in that old description - IIRC it was 3800? - whatever, the 4007 is the same chip. Murray vk4aok
From: Paul Keinanen on 26 Nov 2005 09:25 On Sat, 26 Nov 2005 21:19:18 +1000, Murray <me(a)erewhon.net> wrote: >Frithiof Andreas Jensen wrote: >E.G the CMOS 4007. See the old handbooks for a '100dB >amplifier' based on a RCA chip - there was a wiring >error in that old description - IIRC it was 3800? - >whatever, the 4007 is the same chip. The Motorola McMOS handbook (2nd edition 1974) warns about this usage by pointing out that by cascading three such AC coupled stages, the last stage will be saturated by the noise from the first stage. Paul OH3LWR
From: wa2mze(spamless) on 26 Nov 2005 10:10 Henry Kiefer wrote: > Hi all - > > After my first thread going from "standard" cheap parts for up to vhf > frequency to a discussion about the usefulness of Spice simulator...... I > try it another time hopefully get attention of frustrated co-readers: > > For example the rechtifier diode 1N4007 can be used as a rf switching diode, > for example as rx/tx-switch. This is because it is a pin structure diode. > This type is cheap and you can get it almost everywhere. It shows good > performance for the price. Surely for high-end you should do it with another > type tuned to the application it is made for. But anyway it works in some > circuits. > > Do you know of other interesting devices or circuits good for misuse? > > Best regards - > Henry > > Take one P channel Jfet and one N channel Jfet and connect them in series so the two sources are together, connect the gate of each transistor to the other one's drain. This is known as a lambda connection, and if you plot the voltage vs current from drain to drain you will see a negative resistance region, usually around 3v (depending on the transistors). The circuit will work as a tunnel diode oscillator up to 100-200mhz.
From: wa2mze(spamless) on 26 Nov 2005 10:16 > You must have quite slow fuses in 110 V land if you can do a reliable > ignition without blowing the fuse. For 230 V operation, I would > suggest using a current limiting resistor (such as a large heater) or > an inductance (such as fluorescent light ballast) during the ignition. > When there is a solid arc, the current limiter can be shorted out. > > Paul > Did you know that a carbon arc acts as a negative resistance? Run the arc on DC and put an LC tuned circuit in series with the arc (coil of heavy copper tubing) and you have a powerful oscillator.
From: Rick on 26 Nov 2005 10:43
"Si Ballenger" <shb*NO*SPAM*@comporium.net> wrote in message news:4387be6d.204451325(a)news.comporium.net... > On Fri, 25 Nov 2005 20:48:19 GMT, Al <no.spam(a)wanted.com> wrote: > > >In article <clieo1lq869ialc6um02omsfdt266dvr2c(a)4ax.com>, > > Paul Keinanen <keinanen(a)sci.fi> wrote: > > > >> On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger <jono_1(a)bellsouth.net> > >> wrote: > >> > >> >Take apart a couple of D cell carbon-zinc batteries. > >> > > >> >Wash off the carbon rods. Put each in a wooden clothes pin and connect the > >> >attached ends to the mains voltage (US customers only, please). > >> > >> The problem is that the carbon rod conducts heat quite well, so after > >> a while, any wooden object will catch fire :-). > >> > >> >Tap the free ends of the rods together. Move them apart as necessary. > >> > >> You must have quite slow fuses in 110 V land if you can do a reliable > >> ignition without blowing the fuse. For 230 V operation, I would > >> suggest using a current limiting resistor (such as a large heater) or > >> an inductance (such as fluorescent light ballast) during the ignition. > >> When there is a solid arc, the current limiter can be shorted out. > >> > >> Paul > >> > > > >I would put a 100 watt lamp in series thereby limiting the current. I > >would shave the ends down to points so they heated up rapidly. I put > >them into a hollowed out fire brick and made a cheap furnace. Of course > >don't look at it; it's like looking at the sun. > > The current limiter I saw used a glass pie pan with pieces copper > metal on each side with salty water as the electrolyte. It would > start to steam some when in operation. The furnace was a small > clay flower pot with holes in each side with the carbon rods > sticking inside until they touched. Exactly-when I was a kid we made them like this all the time. As I recall, it came from "700 scientific experiments, with illustrations"... > |