To the question of helicopters or how I spent the weekend
If you bought something, and there is no “Made in China” inscription on it, then you bought a fake.
My readers will be somewhat surprised that I decided not to praise my development, but where to go ... I recently bought at Funny Prices (well this is girlishness, now they are a serious organization and are called “Fix Price”) a fun toy “Flying Ball with Light », You will find numerous links on the Internet yourself.
I played with her for about twenty minutes and overwhelmed me with a desire to find out what is inside the device, which comes from two sources:
- I am an engineer and I wonder how such a toy is arranged (or rather, I already guess how it is arranged and would like to check my guesses);
- I am a businessman in the past and I wonder how the Chinese (I did not write that the toy was made in China, but it seems to be quite obvious) manage to do such things for very little money. I completely forgot to say how much such a toy costs - I bought it for 199 rubles, less than three dollars, Carl.
Since I am alone, and there are two sources of desire, I could not resist for a long time and climbed behind a screwdriver.
ATTENTION: since the toy has a (most likely lithium) battery that is not equipped with a protection board (I did not notice it), any manipulations that could lead to a short circuit or overcharging thereof, the reader carries out at his own risk. The battery, of course, is small and we should not come to a disaster, but who knows. In any case, safety glasses are highly recommended.
We disassemble the case and in our hands we find the insides of the “miracle of technology”, so that we can observe the battery, the engine with a drive on plastic gears, an axis (two pieces) with propellers and a mechanism for stabilizing the plane of rotation (well, I think that figovin is above this is what the propeller does) and, most importantly, the management board for all this wealth. On the board, we observe a chip with 8 legs (I guessed there is MK, but somehow the legs are not enough, it is not enough to control six LEDs), a chip with 5 legs (hmm) and a chip with 3 legs (I guessed it, this is the engine power transistor) . In addition, we have discretes in the form of a power switch, an infrared emitter, an infrared receiver, a charging connector, 6 large and 1 small LEDs, as well as frizz - condors and resistors.
I measure the voltage on the battery, the benefit of wiring is available, and I observe 3.74V (probably lithium), I connect the charging cable and the voltage rises to 4.18V (exactly lithium).
Everything seems to be clear, then the 5-foot microcircuit is just a charger controller (something like 4054) and a small LED signals the charging process. Then a resistor for setting the charging current must be connected to leg 5, I measure its nominal value - 2k3, which corresponds to a current of 400 mA, a full charge (before the LED goes out) is carried out in 15 minutes. We calculate the battery capacity, we get 0.4A * 15min / (60min / h) = 100mAh.
We verify the obtained capacitance by the discharge method, for which we measure the discharge current. Since I don’t want to solder, I turn on the ammeter instead of the switch, bypassing its contacts. The LEDs (all six) lit up, the current went 52 mA, after 2 seconds the rotorcraft engine started and the current ... fell and became 44 mA. Some garbage, not a measurement, cannot connect the motor to reduce current despite the fact that all the LEDs continue to work.
It doesn’t happen, but there is
I measure the voltage on the battery and see that when the engine is running, it drops from 4.1 V to 3.8 V. Yeah, the battery just has a large output impedance, which explains the decrease in current through the switch, and the motor current (judging by the drop, significant) bypasses the ammeter . And for sure, the plus wire of the engine is nailed to the plus of the battery, and the negative has a three-legged microcircuit - a field effect transistor. This solution allows to exclude the flow of a significant current of the motor through the weak contacts of the circuit breaker, but leads to certain inconveniences, about which further. Not including toys, I connect an ammeter between the drain and the source, the engine spun, starting current 1.4 A, steady-state mode - 1.1 A. Then the battery capacity 1.1A * 6min / (60min / hour) = 110mAh - it agrees with the previously calculated.
The motor parameters are determined indirectly - 2.8V * 1.1A = 3W (those who wish can convert to horsepower) - not bad for such a tiny creature. Why there were none of these when I went to an aircraft modeling club as a child. During operation, the engine heats up significantly, but no more than 35-40 degrees. It would be interesting to determine the type of engine, I can’t think of anything other than a collector one, but let’s leave it for later, disassembling the engine will most likely be an irreversible procedure.
The device with 3 legs and the figovin are watching the outside of the case from the board. Since the figovina is surrounded by a tube forming a radiation pattern, this is an infrared sensor. Then the device with 3 legs is the backlight LED, also in the IR range. We trace the paths and find that the device is nailed to the ground and the foot of the MK, and the figovina is nailed to the ground and power, which means that we were mistaken. It’s strange somehow, it is precisely when the finger is brought up to the tube that the engine speed rises, but this is probably a side light.
The most interesting
There remains one mysterious element - a microcircuit with 8 legs, that is, from a functional point of view there are no questions - this is engine control, but what exactly it is implemented on is still unclear. What functions should he implement:
- Initial delay ~ 2 seconds after power up;
- Change of rotation speed by transistor control - PWM modulation with variable duty cycle;
- Reception of a signal from an obstacle sensor;
- Monitoring the battery voltage to avoid overdischarge;
- (last, but not least) engine shutdown when the blades hit an obstacle.
By the way, what good fellows from the point of view of safety - there are engine protection, hand protection is - blades made of soft plastic, there is protection of the structure - fastening of the blades with detachment during mechanical overload. Everything that could have been invented for ease of use has been invented, it remains only to envy the prudence of the developers (well, or to the rich experience of injuries and destruction, then you should not envy).
It seems that there is one more function, but this is not accurate:
6) adaptive correction of the control system, since immediately after launch the helicopter makes significant height fluctuations, but over time their amplitude decreases and it starts to keep an almost stable distance to ground level. If you turn it off and on again, the process repeats, so this is not a consequence of the discharge of the battery.
Let's go back to the control element and estimate possible implementations.
- Each function, in principle, can be implemented on a timer of type 555, but all at once on one case - I definitely can’t, so it’s unlikely.
- On a chip like the quadruple OU 324, you can probably implement all the functions at once, but there is clearly a different case.
- A custom or semi-custom analog chip in a device for $ 3 is not funny.
- But MK will completely cope with all these tasks, this is the main version, the previous ones were intended to demonstrate my broad technical outlook rather.
What resources will be required from MK to implement the listed functions:
- Timer (preferably with PWM mode) to control the motor;
- Comparator (better ADC, but without it) to control engine overload;
- A comparator (again, you can ADC) to control the IR sensor;
- Comparator (you can use BOD) to control the power;
- 4 or 3 free legs to connect the above;
- RAM - 8 registers will be enough, if you take 16 more cells, then you don’t have to figure out why;
- Program memory - 1KB flash should be enough for everything and with a margin.
Probably, in our time it is more difficult to find an MK that does not have the listed resources than satisfies the stated requirements. Based on the case, it can be STM8, PIC, Tiny, MSP430 and so on. But I put on the relatively new MK Taiwanese company Padauk, which have all the necessary resources, but differ from the listed competitors at an incredible price - 3 cents per batch of 300 pieces. For our latitudes, these MKs seem exotic, but for manufacturers from a country located to the south - why not.
The marking on the device case has been carefully removed, but we have indirect evidence. The fact is that MKs of the specified company have a specific power location - 1 and 8 legs (as it was at 555, which hints ...) as opposed to the classic 4 and 8, so we only need to ring the power circuits. Well, then make sure that all the necessary signals are also connected to conclusions that can be identified as general-purpose ports. As for the interval timer, I got excited, he has a power supply pin reversed MK, so that a direct replacement is not possible, although I do not understand why.
Little nitpicking and hitting
PNP: in the course of further study of the circuit, an unexpected (and even somewhat frightening) effect was manifested - when searching (with the help of an auditorium ring) the MK legs associated with the shutter of the engine control transistor, the latter suddenly started - I would recommend to my Chinese colleagues to reduce the value of the locking resistor between shutter and ground (now 27k) to exclude such situations (if this is not part of the protection against reverse engineering).
Well, one more remark - even if the MK makes a decision to stop the engine and goes into standby mode, the LEDs continue to glow and will discharge the battery. Of course, the current is not at all the same as when working, but still significant (tens of milliamps) and is quite capable of overcharging the battery. I managed to land the battery to 2.78 and the voltage continued to drop at a speed of weaving for 2 seconds.
I would add another transistor to turn on the ground of the LEDs or put them directly on the legs of the MK, especially since there are three free ones left.
And here are the results of dialing (in parentheses, the leg function of MK type PMS15A):
- IR radiation sensor connected to leg 4 ();
- The gate of the transistor is connected to the foot 6 ();
- The source of the transistor through a resistor is connected to leg 5 ().
- Earth and power are connected to legs 8 and 5, respectively.
We did not find any contradictions, so it is possible to consider the MK identified with Padauk PS15, it has 64 bytes of RAM, 0.5 kB of one-time program memory, an 8-bit timer with PWM, a comparator and BOD (here it is called LVR) at 2.7V (since the engine shutdown during discharge occurs when the blue LED goes out, it is very similar). Yes, it may be the PMS150C, but it has too much program memory, a whole kilobyte for such a simple task.
Actually, the engineering side of curiosity is satisfied on this, you can draw a diagram of the device, but it is lazy, and there is no need - I still do not intend to produce them, and why it will become clear after the claims of the business part are satisfied. Let's estimate what the equivalent stuffing will cost us, we mean only the electronic part, without the construct.
But do not we count wealthy moles?
The battery is on Ali (I just don’t see the point of looking at domestic resources) there is something similar to our case, the capacity is slightly higher (250 mAh) and is equipped with a protection board - worth 35+ rubles (hereinafter I will give prices in hard currency energy superpower, and not in the worthless obscure green papers of a country that will suffer a final collapse any minute).
The engine (oh, I completely forgot to disassemble it, but apart from the collector motor, no one will adequately respond to voltage changes by PWM modulation, although I saw different opinions on this) - on Ali (see note above) it was found for 20+ rubles.
- I decided to look at 4054 in Platan and was somewhat surprised when its price was no higher than the prices of ChipFind. I somehow got used to the fact that the price of Platan should be divided by 2 and I am glad that I was mistaken. Although the price policy of this supplier is somewhat puzzling to me: we can order the device at a price of 22 from 20 pieces, we can buy from the availability of 39 from 10 pieces, or buy from the availability of 40 from 86 pieces or wait 2 weeks for the purchase of 130 from 1. Of course , I don’t have a company of such a scale as Platan, but I can’t call such a proposal normal. Well, on Ali, it costs 200 rubles for 50 pieces. The total cost of 22 (Platan) /2.5 (Ali).
- MK - probably the most inexpensive component - 2 rubles, still I can not believe in this figure. Although the cost of ownership will be slightly higher - you need to add the cost of soldering, then it will still be more expensive than the transistor.
- IR emitter (TSAL6100) - 6/6.
- IR receiver (included in the set for 6 rubles) - / 3.
- transistor 20V, 2A (n327) 5/4.
- 6 bright LEDs in 3 colors (HL3010) 2 / 0.2 * 6 = 12 / 1.2.
- resistors and capacitors of size 0603 total 16 pieces 0.3 / 0.2 * 16 = 4.8 / 3.2.
- switch (3 / 0.4) / power connector (8/8) / and power cable / 8.
- printed circuit board (DPP + M + 2Sh) 0.4dm * 0.2dm = 0.08 * 170 (Resonite) / = 13 /.
- mounting the board 5 + 8 + 3 + 2 + 3 + 6 * 2 + 25 * 2 + 3 + 3 = 88 solder points * 0.5 = 44.
In total, we get 189/153 rubles (of course, the calculation cannot be called absolutely accurate, but I estimate the error at 30 percent) and the conclusion is disappointing - only the electronics will take away almost the entire sale price from us, and all the construction, logistics, producer’s profit, seller’s profit and taxes, so the chances of making such a helicopter at this price differ from zero by a negligible amount.
Well, the last remark: this particular balloon is sold on Ali for 206 rubles with a remote control and with transfer for 250 rubles, a similar product (with a slightly different case, in the form of a helicopter or a devil, and not a ball) is sold in the same 350+ rubles, which kind of weird. In general, I was probably just lucky with the purchase, which is indirectly confirmed by the behavior of my wife, who the next day bought three more copies of this toy - one for each grandson and granddaughter, and she is not inclined to buy any garbage at inflated prices.
The general conclusion from the above will be somewhat unexpected:
God bless China (well, America at the same time).
PS I am enclosing a photograph in which I (unsuccessfully) tried to restore the circuit, it may come in handy:
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On the advice of one of the commentators, he began to put section names
- 83.6% Oh, class, finally it became possible to read 159
- 11.5% Move in the right direction, but need a subtitle for each paragraph 22
- 4.7% And in figs they gave up, before it was better 9