Gary:
An alternative is to use either quad array photo-Darlingtons packages for
low-current interface applications...
http://www.vishay.com/docs/83650/83650.pdf
Or PhotoMOS, to directly drive relays or other moderate-current devices.
The diode section of these devices can be powered by one unit, while the
transistor side references power from the interfaced device, resulting in
excellent optical isolation between equipment.
http://pewa.panasonic.com/pcsd/product/pmos/pdf/aqw21_.pdf
Granted, a small array of packaged MOS devices can be a bit pricey,
However, as a substitute, the previous photo-Darlington could be used to
drive a simple and inexpensive medium-power MOS transistor.
In either case, there's a broad range of optical devices available today in
several different packages to allow for power supply and signal line
isolation between equipment.
Paul, W9AC
----- Original Message -----
From: "CSM(r) Gary Huber" <glhuber@msn.com>
To: "TenTec Reflector" <tentec@contesting.com>
Cc: "DXLab Group" <dxlab@yahoogroups.com>
Sent: Tuesday, June 15, 2010 1:44 PM
Subject: [TenTec] Bandswitching the 253 with OMNI VII or Orion
I recently purchased a new OMNI VII and had to figure out how to band
switch my model 253 Automatic Antenna Coupler (my Omni VI+ had the
capability). DXLab Suite Commander can take the Omni VII frequency
information and with a device table unary code output a 4.4 VDC on one pin,
2-8 of the computer's parallel port (DB-25). The seven pins can drive pins
2-8 of a ULN2803 which outputs a higher current / voltage on pins 12-18
providing the 10-14 +VDC at 300 mA needed by the 253 tuner.
A ULN2803 is an Integrated Circuit (IC) chip with a High Voltage/High
Current Darlington Transistor Array. It allows you to interface TTL
signals with higher voltage/current loads. In English, the chip takes low
level signals (TLL, CMOS, PMOS, NMOS - which operate at low voltages and
low currents) and acts as a relay of sorts itself, switching on or off a
higher level signal on the opposite side.
A TTL signal operates from 0-5V, with everything between 0.0 and 0.8V
considered "low" or off, and 2.2 to 5.0V being considered "high" or on.
The maximum power available on a TTL signal depends on the type, but
generally does not exceed 25mW (~5mA @ 5V), so it is not useful for
providing power to something like a relay coil. Computers and other
electronic devices frequently generate TTL signals. On the output side the
ULN2803 is generally rated at 50V/500mA, so it can operate small loads
directly. Alternatively, it is frequently used to power the coil of one or
more relays, which in turn allow even higher voltages/currents to be
controlled by the low level signal. In electrical terms, the ULN2803 uses
the low level (TTL) signal to switch on/turn off the higher
voltage/current signal on the output side.
The ULN2803 comes in an 18-pin IC configuration and includes eight (8)
transistors. Pins 1-8 receive the low level signals, pin 9 is grounded
(for the low level signal reference). Pin 10 is the common on the high
side and would generally be connected to the positive of the voltage you
are applying to the relay coil. Pins 11-18 are the outputs (Pin 1 drives
Pin 18, Pin 2 drives 17, etc.).
see http://www.dxlabsuite.com/commander/Help/Devices.htm and
http://www.dxlabsuite.com/commander/Help/Configuration.htm#Device tabs
Best regards,
CSM(r) Gary Huber - AB9M
9679 Heron Bay Rd
Bloomington, IL 61705
(309-662-0604)
www.csm-gh.com
glhuber@msn.com
gary.huber@us.army.mil
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