[RFI] Touch lamps going crazy
Hare, Ed, W1RFI
Hare, Ed, W1RFI" <ehare@arrl.org
Tue, 7 Apr 1998 11:07:00 -0400
Now that I have another minute in my rather busy schedule, I will add a bit
of information. Touch lamps use a free-running oscillator usually running
at 50-200 kHz or so, a touch plate, and a simple circuit that senses a
change in frequency. Naturally, the touch plate can also pick up nearby RF.
When it does, the sense circuit thinks the frequency has changed and the
lamp changes state. RF can also be picked up on the power lines and
conducted into the lamp circuitry.
The cures outlined in QST generally consist of inserting a resistor or
inductor in series with the touch plate. This seems to work in about half
of the cases, especially if the RF level is not significantly above the
threshold of interference. In some other cases, using an ferrite core made
from #43 material (upper HF, VHF) or #75 or -J material for lower HF, with
about 10 turns of the lamp's ac cord wrapped onto the core, may also effect
a cure. In rare cases, a 'brute-force' type ac-line filter may be helpful.
The advice given here has been to toss the lamp. This is probably a good
idea, for a number of reasons. In most cases, it is NOT a good idea to
modify your neighbors' equipment. The potential liability is not worth the
risk. There are dangerous voltages inside the lamp, and you may be
electrocuted trying to fix it, or your cure may inadvertently put 110 v onto
metal parts of the lamp. (It happens, as the bumper sticker says.) In some
cases, the cure may cost more than the lamp is worth.
The FCC is pretty clear about touch lamps and other "non-radio" devices. If
non-radio devices pick up RF signals, they are improperly functioning as
radio receivers. The FCC suggests that the owner of the device should
contact the manufacturer for help, although this rarely works out.
73 from ARRL HQ,
Ed Hare, W1RFI
ARRL Lab
----------
>From: Hare, Ed, W1RFI
>To: Bryan; rfi
>Subject: RE: [RFI] Touch lamps going crazy
>Date: Tuesday, April 07, 1998 10:25AM
>QST articles on touch lamps:
>
>qst1985.txt:Rfi And Touch Controlled Lamps ... May P45
>qst1986.txt:More On Rfi To Touch Controlled Lamps ... Jan P49
>qst1987.txt:Touch Lamp Transceiver ... Feb P43
>qst1988.txt:Taming Touch And Glow Lamps ... Mar P42
>qst1993.txt:Touch Lamp RFI Cured (Hallock): May, 78
>qst1993.txt:Touch-Control-Lamp RFI (Wiley): Feb, 53
>qst1995.txt:Low-Pass Filter Cures Touch-Lamp Interference (Birgenheier):
>Apr, 72
>qst1995.txt:Stalking the Elusive Touch-Controlled Lamp (McCook): Feb, 66
>
>73, Ed Hare, W1RFI
> ----------
>>From: Bryan
>>To: rfi
>>Subject: [RFI] Touch lamps going crazy
>>Date: Monday, April 06, 1998 5:12PM
>>
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>>From: Bryan <bryan@prodistributors.com>
>>Subject: [RFI] Touch lamps going crazy
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>>
>> Well, we got new furniture last week and the new
>>credenza that went in the bedroom has a pair of touch
>>operated lamps built into it. Really handy, all you
>>have to do is just touch the control and they go
>>low-med-high and then off.
>>
>> Problem is that each I time I hit key the mike
>>or key on the TS-940 the lights go low-med-high off, low-med-
>>high-off, and sequence repeats itself with each voice
>>peak or every sequence on the keyer. Not to neat when you are
>>calling the H40 at 2:30 in the morning and the lights are
>>flashing like crazy in the bedroom.
>>
>> OK guru's....how about a fix for flashing lights??
>>
>>Bryan W5KFT
>>
>>
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>>
>
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