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Monster Media 1994 #2
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Monster Media No. 2 (Monster Media)(1994).ISO
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ham
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hcomckt.zip
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HCOMCKT.TXT
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1994-06-29
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7KB
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141 lines
Here are two opto circuit I've been playing with for HAMCOM/JVFAX.
They virtually eliminate all computer induced rfi. I've been using
a five foot serial cable and twenty foot audio cable with this
circuit and the results are truly remarkable with JVFAX.
I've used the first circuit successfully, but recommend using the second.
The first can be built with common Radio Shack parts. The second requires
a little more uncommon LM358 and TIL181. The Radio Shack opto RECEIVER
is only rated at 20v but used at 24v and could eventually burn out.
It also may introduced problems since the +9v is not regulated and induces
error into the reference op amp output ... even though it seems to work well.
Perhaps some engineers out there may have some advice.
===============================================================================
+9v
|-------- +9V ________ DTR
9 volt batt. --------- | 1uf | |
----- === | |
| | [ ] 1K [ ] 2.2K
|-------- | |________DSR
GND |C |
+9v ___ |/ - C
| \ / /\/ |
.1 uF |\ | ----- |\-> A
>------| |--*-----------------------|- \ |A |
| |741 \______| |
| | / --------RTS
| --------|+ /
| | |/ |
[ ] 100K [ ] 100K |
| | GND
*--------------*
| |
+9V | |\ |
| -----|- \ |
| |741 \___| +4.5 REFERENCE
100K [ ] | /
|-----------|+ /
100K [ ] |/
|
|
GND
===============================================================================
INFARED EMITTER INFARED DETECTOR
(clear) (dark)
---------- ----------
| | | |
| |__ | | | |__ | |
| | | | | | | |
| -- | | | -- | |
| | | | | | | |
---------- ----------
| | | |
| |
These are available at Radio Shack as a pair for $1.99 (#276-142).
This shows which is the Anode and which is the Cathode, not clear on
the package.
The LED and DETECTOR must be positioned right up against each other and
exactly aligned to get maximum light transfer. The sides with the little
lense like dots must be placed together.
===============================================================================
I'd recommend this second circuit for more stability and possibly accuracy.
RS232 connector size ----> 25 9
+9v -- --
|
o +9V ----o DTR 20
/ SPST SWITCH | |
o SW1 | |
| R1 [ ] 1K R2 [ ] 2.2K
9V *-------- | |
BATTERY | | | |----o DSR 6
--------- --- C1 |1 TIL181 |5
----- --- 1UF .......................
| | . |C U2 |C .
* ------- . ___ |/ - .
| . \ / /\/ | .
GND . ----- |\-> .
+9v . |A |A .
| .......................
AUDIO 100 nF 6|\ |8 |2 |4
o------| |--*------------|- \ | |
| | U1 \_7____| ----o RTS 4
| 5| /
| ----|+ / LM358 2|\
| | |/ |4 ---|- \
R3 [ ] R4 [ ] | | | U1 \_1___ (not used)
GND 100K | 100K| | | 3| /
o-----------*-------*--------*------------*---|+ / LM358
| |/
GND
===============================================================================
| ** NOTE** |
| After constructing, measure LM358 pin 7 with no audio on the input. |
| It should be high (~8v), if it is low (~0v) it will drain the battery |
| in only 20 hours or less. |
| |
| To correct this: Disconnect R1 from +9v and reconnect to U1 pin 7. |
| Disconnect U1 pin 2 and reconnect to GND. |
| |
===============================================================================
The LM358 is a single supply opamp and can be substituted with the LM2904,
LM158, or LM258. (The dual supply 741 can not be used as a substitute.)
The opto isolator IC can be substitued for many other types. The 4N35 has
been tested successfully. The discrete infared emitter/detector from
Radio Shack has been tested successfully.
I tried to use a darlington opto (TIL113), but couldn't get it to work.
A darlington opto circuit would only require 1.5ma average. That would
make battery life about 133 hours. Maybe I'll try again later.
===============================================================================
MORE NOTES:
The 9v battery could be substitued with a 9 or 12 vdc adapter. However I've
found the clearest pictures occur when both the radio and HAMCOM are running
off batteries ... at 6am 8).
A 9v battery should last about 50 hours while audio is present (assuming 200ma
hours for a battery). If no audio is present the battery will last 400 hours.
The battery life could be a problem for people who leave HAMCOM running
all night using the timed FAX option. Battery would only last a week.
If you have any advice or knowledge that could improve this, please let
me know.
copeland@metronet.com