by acl » Tue Aug 11, 2020 8:45 pm
Thanks Steve for the information. Just an idea but could you just use a series of comparitors to do the 'front end job' of the a to d conversion on the SSTV convertor ? then feed to a port
The LM3914 / LM3915 / LM3916 are identical except for the ten resistor divider inside each part.
LM3914 - linear steps, scaled by a resistor divider consisting of ten 1000 ohm resistors.[1]
LM3915 - 3dB logarithmic steps, scaled by a resistor divider consisting of 6630, 4690, 3310, 2340, 1660, 1170, 830, 590, 410, 1000 ohm resistors.[2]
LM3916 - VU-meter steps, scaled by a resistor divider consisting of 1087, 970, 864, 769, 1298, 1031, 819, 923, 1531, 708 ohm resistors.[3]
All the devices in this group operate with a range of voltages from 3-35 V, can drive LED and VFD displays.[4] They can provide a regulated output current between 2-30 mA to directly drive displays.
Internally, each device contains ten comparators and a resistor scaling network, as well as a 1.25 volt reference source. As the input voltage increases, each comparator turns on. The device can be configured for either a bar-graph mode, where all lower-output terminals switch on, or "dot" mode in which only one output goes on. [5] The device is packaged in an 18 pin dual in-line package or in a surface mount leadless chip carrier.