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Actually, the servo position (not its speed) is controlled by the sawtooth voltage.
The receiver supplies current based on the back emf up to the stall current that's about 300mA for small servos.
I'll definitely try the circuit you posted. Thanks.
The stiff wing flapping up and down will not fly. A bird's wings are flexible so they are partially folded and go past the air when they go up and they open and hold and force held air down and back when they go down.
Actually, the servo position (not its speed) is controlled by the sawtooth voltage.
The receiver supplies current based on the back emf up to the stall current that's about 300mA for small servos.
I'll definitely try the circuit you posted. Thanks.
I need to know what Servo voltage corresponds to down.
I assumeed it was 0 and my quick fix gave the offset to near 0V on negative peak, but is that down or up.
I also posted a link with my design you can try and see how it works with the POTs... YOu can control the simulation speed to be exactly "realtime" or slow motion or fast i.e. 1 second per update. java approval popup will occur.
Mosaic: I specifically said in post #18 that the Robara is NOT AN ORNITHOPTER. Do you know the difference between a wing that flaps just for looks (to train hawks) and an ornithopter? If you're an expert on model designing, building and flying, pleeeeeeeeeeaaaaaase help me!!! How can I improve my Robara??? (Not "robird", thanks!)
Tony: I can choose to make either 0 or 6V wing up or down. It's just a matter of reversing the servo.
The servo position is in realtime with the voltage (up to a certain frequency, of course).
Some tweaks done just now after dinner. Take it for a spin.
Improved full scale swing to 6Vpp
Offset pot can exceed 6V tho since you specified a 9V bat. That can be fixed if needed or just adjust pot.
Coarse flap per sec. (fps) has a 50:1 range down to 15 sec. cycle for show N tell
Sawtooth defined with fast up flap regardless of flap rate or up to 1/3 sec cycle for almost 50:1 range
Fine fps is just for 2:1 range control and fine tuning.
So coarse can go from stop to full speed quickly
and fine can adjust 1 to 2 fps or 1.5 to 3 fps. for example.
YOu can increase Vpp to exactly 6Vpp by reducing 70K by a few percent with 1M in parallel but much lower and it will stop oscillating. when it exceeds hysteresis.
This also depends on saturation of OpAmp with ~8V out and battery level, so not perfect yet. ( perfect would use a 5V reference like 78L05)
Similarily if Coarse is brought to minimum it will exceed hysteresis and stop flapping and slowing drift to near null.
Plastic film caps will give the best performance over ceramic. for long time constant.
Note 5 channel sliders on right side . Simulation speed, Current (disabled) and 3 Pots.
Values can be scaled to use all 10k or 100k pots linear or log.
I heard an engine (or electric motor?) driving a propeller on some model flapping birds.
The huge ORNITHOPTER flew very well by flapping its wings without an engine and propeller.
audioguru: An ornithopter must have a motor to drive the flapping wings. Wingbeat uses a quiet EDF (Electric Ducted Fan) like the ones shown below.
There are some model birds that are soarers. Their wings don't flap. They get their lift from rising winds near cliffs or hills.
Just a test point for adjusting the fixed R to variable R sensitivity to suit your needs for frequency range. The ratios of R's affects sensitivity. thus I inserted the Fixed R to improve the full range to be more useful.
If you wanted to regulate the characteristics to be battery tolerant from 9.5V to 7V then a 5V zener could be inserted at test point. or a white or blue and Red or yellow LED in series for same 5V max instead of 8 that tracks Vbat.
Right about the LEDs. I use a few diodes.
Electric model planes use LiPo batteries, so their voltage is a multiple of 4.2V at the start then 3.7V when the batteries are low.
Most of my planes use a 3 cell LiPo that starts at 12.6V. But I can tap into one of the battery connectors (JST) and get 8.4V to start.
So, if the batteries get lower, does that mean the sawtooth amplitude will decrease proportionally?
Could I use a 6V zener somewhere to get a steady voltage at the amps?
The problem with this design you found is that everything is dependant on supply voltage. and the Op amp is not very precise with offsets from supply rails on the output.
forget about the diode trick, I overlooked something.
but if you really want a universal solution pick a universal voltage regulator with 0.5V drop max. like 78R05. (5V) or some other universal voltage. just below dead battery Vbat
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