Unusual functions of cheap parts
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From: skavanagh72nospam on 27 Nov 2005 10:02 Martin wrote: > > I once built an HF transceiver that used CMOS logic chips for all > > functions except an audio low noise amp and a voltage regulator...with > > further thought those two could likely be done with CMOS logic too. > > > At least the audio amp, this is nice to build with some Inverters (4069) > with resistive Feedback. Most of the audio section was done that way. But the product detector had low impedance output and the CMOS amp was too noisy at 50 ohms. A transformer might have done the job but a common-base amp seemed more practical and less prone to picking up hum. Steve
From: Martin on 27 Nov 2005 18:50 Am Sat, 26 Nov 2005 22:35:18 -0500 schrieb Phil Hobbs <pcdhSpamMeSenseless(a)us.ibm.com>: > Martin wrote: >> Am Fri, 25 Nov 2005 22:13:38 -0500 schrieb Phil Hobbs >> <pcdhSpamMeSenseless(a)us.ibm.com>: >> >>> Si Ballenger wrote: >>> >>>>> 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. >>>> >>> >>> As a boy, I used an electric teakettle as a ballast for a two-D-cell >>> carbon arc lamp--worked great. >>> >> An electric arc with just 3V from two D-cells? I thought the arc needs >> at lesat 20V burning voltage. >> > > It ran off 120 V. Parse the sentence as "two D-cell-carbon arc lamp." > An earlier poster talked about building AC-powered arc lamps using the > carbon rods from dry cells. > OK :-) I liked to do that myself, but not from our 230V mains power, but with a transformer, 22V, and 30A short circuit. -- Martin
From: Winfried Salomon on 27 Nov 2005 21:01 Hello Jim, Jim Thompson wrote: [...] >>btw, do you know a standard complementary pnp-transistor for the 2N2369, >>such like 2N3905 but with higher ft and less feedback capacitance? It >>seems that the manufactorers have almost no data on their internet pages. [...] > > > A 2N2369 is a gold-doped NPN, gold-doped to kill storage time and > improve recovery from saturation. I don't recall any PNP device with > gold-doping... or the equivalent. thank you, then I suppose the 2N3905 oder 2N2905 are fitting for a large signal amplifier. mfg. Winfried
From: Rich Grise on 28 Nov 2005 17:21 On Fri, 25 Nov 2005 00:43:52 -0800, Bob Monsen wrote: > On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger 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). >> >> Tap the free ends of the rods together. Move them apart as necessary. Very >> bright! Much brighter than you are. > > One of the MIT EE course videos on the web shows a demonstration of AC > across a pickle... it is an interesting effect. Not sure how the pickle > tastes afterward. Cooking hotdogs with AC is similar, but the pickle gives > off a much nicer translucent flickering glow. Very pretty. > But who wants a cooked pickle? ;-) Thanks, Rich
From: John Perry on 28 Nov 2005 18:24
Rich Grise wrote: > ... > > But who wants a cooked pickle? ;-) > My ethnic Russian daughter-in-law, just arrived from Tatarstan, made a Russian soup, into which she chopped several dill pickles. Wonderful stuff! John Perry |