tlc551 CPO - runs off the power supply of a sound card MIC JACK

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Chuck Vaughn

May 19, 2023, 10:55:24 AM5/19/23
to iCW - internet CW
tlc551cpo.pngsee video description for more info on the setup...


According to The Internet, 95% of electronic projects can be done with an op-amp or 555 timer chip. We're not so sure about it, but the 'triple nickel' (as we like to call it after we've had a gin&tonic) does come in handy for many simple analog or digital circuits. The classic part number is often referred to as the "NE555", and here we've got a modern spin on the classic.

The TLC551 is a monolithic timing circuit fabricated using TI's CMOS process, for lower power, wider voltage range, and higher speeds compared to 'classic' NE555s made with TTL. The timer is fully pin-compatible with CMOS, TTL, and MOS logic and operates at frequencies up to 2 MHz. Compared to the NE555 timer, this device uses smaller timing capacitors because of its high input impedance. As a result, more accurate time delays and oscillations are possible.

Power consumption is low across the full range of power supply voltage, so  you can run it on even a single AAA, instead of needing a proper 5V or 9V power supply.

Like the NE555, the TLC551 has a trigger level equal to approximately one-third of the supply voltage and a threshold level equal to approximately two-thirds of the supply voltage. These levels can be altered by use of the control voltage terminal (CONT). When the trigger input (TRIG) falls below the trigger level, the flip-flop is set and the output goes high. If TRIG is above the trigger level and the threshold input (THRES) is above the threshold level, the flip-flop is reset and the output is low.

Comes as a single DIP chip for breadboard-friendly operation.

The reset input (RESET) can override all other inputs and can be used to initiate a new timing cycle. If RESET is low, the flip-flop is reset and the output is low. Whenever the output is low, a low-impedance path is provided between DISCH and GND. All unused inputs should be tied to an appropriate logic level to prevent false triggering.

While the CMOS output is capable of sinking over 100 mA and sourcing over 10 mA, the TLC551 exhibits greatly reduced supply-current spikes during output transitions. This minimizes the need for the large decoupling capacitors required by the NE555. The TLC551C is characterized for operation from 0°C to 70°C.


May 19, 2023, 1:28:24 PM5/19/23
to iCW - internet CW
Here is another example of this TLC551 CPO being keyed by a CW KEYER's rig keying RCA JACK output
to the CHIP's PIN4/PIN 8   and also cleaning up the harsh square wave 800 hz sidetone using a single audio bandpass filter
from RECRI KEYER's SDR MODULE   'filt' 

Chuck Vaughn

May 19, 2023, 2:42:21 PM5/19/23
here is another example using the TLC551 for a complete midi input keyed  iambic cw keyer:

see video description for more info on that setup...


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Chuck Vaughn

May 23, 2023, 6:21:10 AM5/23/23
key TLC551 Timer Chip CPO - REAPER PLUGins analyze & regenerate TLC551 square wave into pure sine wave with raised cosine edges
brief demo of using REAPER by itself to analyze an incoming square wave morse code signal from a CW KEYER/paddles,
that is KEYing a TCL551 TIMER CHIP SQUARE WAVE OSCILLATOR(TLC551 pins 4 & 8)
and then REAPER PLUGINs re-CREATE and output a new cloned, identical CW ELEMENT,
with an adjustable pure sine wave CPO that has raised cosine edges


May 25, 2023, 6:25:38 AM5/25/23
to iCW - internet CW
Raspberry Pi iAmbic CW Keyer:
BUILT with the following...
TLC551 OSC.,
TriggerMidiMono &
Recri Keyer miDi CW kEYER


May 25, 2023, 8:57:52 AM5/25/23
to iCW - internet CW
Here is an example using  TWO   TLC551  TIMER CHIP OSCILLATORs 
operating at VERY different frequencies ,   both running off the MIC JACK POWER SUPPLY
one TLC551 performs iambic keying,  the other  TLC551 performs STRAIGHT KEY keying:


Jun 13, 2023, 1:16:46 PM6/13/23
to iCW - internet CW
here is another example keying the TLC551 square wave CPO, into a PI4 usb mic adapter...
a single GSTREAMER SCRIPT cleans up the square wave and converts it to pure sine wave with raised cosine edges:
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