I'm familiar with RC. I've been doing it since 1980. The one problem with PWM used in radio control is that it does not automatically adjust the pulse width/frequency as the battery voltage drops.I buy Micro Ready to Fly radio controlled model airplanes at my local hobby store. They are made by E-flite and their main USA distributor is Horizon Hobby.
The coreless brushed motors are cheap and have a very short life. They were originally used to occasionally open and close a CD tray or occasionally operate a vibrator in a phone. The brushes wear out or burn out soon when running continuously on a model airplane or toy helicopter/drone.
The "beginners" RC airplanes use a single-cell Li-Po battery that charges to 4.2V, averages 3.7V during a discharge and the driver circuit disconnects the main motor when the battery voltage drops to 3.0V (leaving the receiver and servos working). The cheap motors need gears.
Brushless motors powered from one or two Li-Po cells are available in model airplanes used by skilled users. They do nor burn out or wear out and "last forever".
PWM is used to control motor speed with barely any losses or heating. The brushless motors produce lots of torque and do not use gears.
True. No argument here on the voltage drop comparison between battery and capacitor.The voltage of a discharging Li-Po battery drops gradually. The voltage of a discharging capacitor drops sharply at the beginning of a discharge. I think the capacitor instead of a battery is your problem and you might not notice the gradual voltage drop from a battery.
Now you provided a lot of very useful informations. Application: Your flight model.circuit footprint and circuit weight. I have failed to emphasize these constraints because the original voltage regulator circuit met those requirement.
Hi,
Now you provided a lot of very useful informations. Application: Your flight model.
I repharse the true goal as "flight model control"
Good information, too: you want the control to be independent of battery/capacitor voltage.
Also extremely good informations: the numbers for weight and size. 1.5g is "solid" information all over the world and for all electronics designers.
Well done.
A short explanation of my way of designing (without saying it's the best one and everyone needs to adopt this)
In the beginning with the given information I was focussed on the linear voltage control. Pure schematics and function.
But now with the given infirmations I think beyond schematics ... I think of a "flight model control system".
The difference is: The schematics does not care about weight, board size and heatsink ...
Now knowing the requiremens: a linear solution is not small nor leight weight anymore, because it needs a lot of board space, maybe even a heatsink.
Additional information: All the dissipated heat needs to be supplied by your battery. So the less heat, the longer the flight time.
SMPS: It's expected that you do simple internet search on your own. Not meant rude. It's just that we don't know what "vocabulary" you are familiar with.
Now in short: Switch Mode Power Supply. Functionally "switching" is the alternative for "linear" regulation. Usually done with regulated PWM. Low power loss.
Again: an SMPS is not the first thing I recommend. I rather recommend a motor control.
If I had to do the design, I'd most probably go with a tiny microcontroller including ADC and PWM.
Klaus
An objective view...A plea to all. If you are going to use an acronyms, please define it at least once. The same acronym can mean different things to different people.
No, I hadn't considered solar cells. There are two reasons for that. The first is that capacitors can be used indoor and I'm not aware of any solar cells that function very well indoors. The second reason is that this forum topic deals with problem solving a voltage regulator for use with capacitors.have you considered using solar cells instead of super capacitor?
Ultralight solar cells designed to drive drones
Researchers have shown perovskite solar cells just 3μm thick can power miniature model aircraftwww.chemistryworld.com
pulse width would have to be adjusted continually as the capacitor voltage drops.
Brad, I'm a electronics dummy. I didn't understand everything you said.PWM is efficient because the load is switched On-and-Off.
Suppose your control circuit is pulsed DC, and you have a way to increase duty cycle as supply voltage (cap voltage) drops?
The 555 IC is able to operate down to about 3VDC. Voltage applied to pin 5 sets duty cycle.
Say you fix pin 5 at 3V, and start out with the supply capacitor initially charged to 5V. Duty cycle automatically changes as the relationship between these volt levels changes.
Output pulses drive a pass transistor.
View attachment 178288
Yes I was suggesting the 555 has a chance of doing what you need. Or else a lesser-voltage cousin (from replies in your other thread). Configure it as an oscillator (same as pulse generator). Set the frequency to whatever works well with your motor.I think that you said the 555 chip should work. Is that correct?
You mentioned pin 5. Is pin 5 labeled 'ctl' on the circuit diagram?
"Suppose your control circuit is pulsed DC, and you have a way to increase duty cycle as supply voltage (cap voltage) drops?" I'm lost. It appears that this is a question but I'm not sure what it's asking. Or, are you saying that the 555 with a pulsed control input would increase the duty cycle with a dropping capacitor voltage?
What is the source of the 3.1 V in the upper left and the +3V at the ctl pin? I only have the capacitor as a power source. A typical voltage range for a hybrid capacitor is from 2.3v to 4 volts.
Thanks much for the link. I hate to admit it but I learned all that stuff in college. The only trouble is/was that was the last time I had used it and I had forgotten most of it.Hi GH,
I don't want to bombard you with yet more information while you are still processing the avalanche received so far, but, inside 'Thermal Derating Curves for Logic Packages' is the coffee cup - it's a short read that is highly palatable (even I understood it first, ...or maybe second, time around) and directly related to the main issue of your thread.
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