Re: X-10 RF meter (was Re: XTB II Review)

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

>"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
>news:459b1d21.9944265@xxxxxxxxxxxxxxxx

>> It might be possible to build one for under $15 but I'm not sure how it
>> might be affected by being handheld while searching for a transmitter.
>>
>> The RF receiver modules that I specified the BX24-AHT and roZetta have a
>> linear output pin which can be used as a signal strength indicator. You
>> would want an inefficient antenna, a battery and you might get buy with
>> a  multimeter as the readout. More likely you would need a PIC and an
>> LED or some type of visual indicator.

Using a PIC would require programming which eliminates many folks that
could otherwise do a one-off DIY implementation without waiting  (perhaps
forever)for someone else to do the programming.

The output could be handled by an off-the-shelf National LM3914 (linear)
LM3915 (log) or LM3916 (VU) Dot-bar graph driver chip which takes analog
input and drives up to 10 LEDs (or 20 or 30, or more if you cascade
LM391x's) with linear, log or VU-meter response.

So a one-off X-10 RF signal strength sniffer/meter could indeed be
constructed *without* programming for ~$15 or so (depending in part on what
is already in your electronic junk box).

1- Radiotronix RCR-315-RP
http://www.radiotronix.com/datasheets/rcr433rp.pdf  $5.66 from
www.Mouser.com Part 509-RCR-315-RP tuned to 310 Mhz as Dave suggests.

1- National LM3915 analog-in 10-step log LED Bar-Dot display driver
http://www.national.com/pf/LM/LM3915.html  There are also  LM3914 (linear)
and LM3916 (VU meter) versions which may provide better matches to the RF
receiver's non-linear analog output which is non-linear. No good reason one
could have both linear and log outputs. $2.64 from www.Digikey.com part
LM3915N-1-ND

1- 5-volt regulator such as LM78L05 or equivalent
http://www.national.com/pf/LM/LM78L05.html
$0.36 from www.digikey.com part LM78L05ACZFS-ND


1- 9 volt to 12 volt battery with holder/clip
1- 4.7 ufd tantalum cap
1- 0.01 ufd ceramic cap
1- 10 ufd electrolytic cap
10 LEDs
1- 1.24K 1/4 watt resistor
1- 8.06K 1/4 watt resistor
(or substitute 10k multiturn pot for above. See LM391x data sheet.))
1- General purpose project pcb (eg Radio Shack)
Case if wanted.
Antenna materials

HTH ... Marc
Marc_F_Hult
www.EControl.org