Unusual functions of cheap parts
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From: John - kd5yi on 26 Nov 2005 21:53 "Henry Kiefer" <otc_friend(a)gmx.net> wrote in message news:4388fc28$0$20854$9b4e6d93(a)newsread2.arcor-online.net... > Yes Martin. I've seen that and a refrigerator can it too! > - Henry > > > "martin griffith" <martingriffith(a)XXyahoo.co.uk> schrieb im Newsbeitrag > news:ft1ho1du06kls05nge61k2so27j1b41rk3(a)4ax.com... >> On Thu, 24 Nov 2005 09:40:27 +0100, in sci.electronics.design "Henry >> Kiefer" <otc_friend(a)gmx.net> 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 >> > >> Switching a 20 year old 24v weller soldering iron on and off is a good >> test for seeing if an 8051 cpu board is EMC proof >> >> >> martin > But, it's a bit easier to degauss your picture tube with a soldering gun than with a refrigerator. John
From: Martin on 26 Nov 2005 22:21 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. -- Martin
From: Phil Hobbs on 26 Nov 2005 22:35 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. Cheers, Phil Hobbs
From: John Larkin on 26 Nov 2005 22:44 On Sat, 26 Nov 2005 21:40:53 -0500, Boris Mohar <borism_-void-_(a)sympatico.ca> wrote: >On Sat, 26 Nov 2005 15:41:27 -0800, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen" >><frithiof.jensen(a)die_spammer_die.ericsson.com> wrote: >> >>> >>>"Henry Kiefer" <otc_friend(a)gmx.net> wrote in message >>>news:4385b3b1$1$27887$9b4e6d93(a)newsread4.arcor-online.net... >>> >>>> Do you know of other interesting devices or circuits good for misuse? >>> >>>LED's work both ways, as a light emitter and a photodiode. >>> >> >>And optocouplers can do interesting things: >> >>Very simple high-voltage opamp, up to 400 volts p-p. >> >>Isolated totem-pole driver, from a few volts up to 400. >> >>Current limiter. >> >>Low-leakage diode, sort of like an LED painted black. >> >>John > > A latch. Right, if CTR > 1. John
From: Martin on 26 Nov 2005 23:13
Am Sat, 26 Nov 2005 16:16:27 +0000 (UTC) schrieb Matthias Weingart <mwnews(a)pentax.boerde.de>: > John Devereux <jdREMOVE(a)THISdevereux.me.uk> wrote in > news:8764qh82fw.fsf(a)cordelia.devereux.me.uk: > >> ehsjr <ehsjr(a)bellatlantic.net> writes: >>> Henry Kiefer wrote: >>> > Do you know of other interesting devices or circuits good for >>> > misuse? Best regards - >>> > Henry >>> >>> An LED as a shunt regulator. Also, as a varicap. >>> Ed >> >> Also a photodetector that is insensitive to long wavelengths >> (because of the high bandgap). > > To save power, use the LEDs of a backlight to measure the ambient light > to decide to switch the backlight on or not. > But how to decide to switch it off? I think there you have to sample - switch of for a short time and test. This could give a flickering backlight. -- Martin |