Explorer-2

A day after the publication of the article Explorer-1 (My Spirit), I began to develop the next version of the device. On the advice of habrayuzers, outlined what needs to be added to Explorer-2:

1. Two-way communication.
2. Camera
3. Duplicate sensors.
4. More sensors.
5. The sane case.
6. Sleep mode.
7. The power source is more serious than the seedy “crown”.

I expected to do all this in a couple of weeks. However, in the end, development from scratch took a whole month. Too many pitfalls were detected at every step.


First of all, the necessary sensors and accessories were purchased:Analog temperature sensor LM335Z, digital temperature sensor DS18B20, digital temperature and humidity sensor DHT11, photoresistor VT93N1, atmospheric pressure sensor BMP085 from Bosch, camera drive - MG-90S.

1. Two-way communication .

This is the most important point that distinguishes the 1st version from the 2nd. Without two-way communication, it is impossible to control the device by definition, and completely relying on automation is risky.
First of all, I made a connection between the two Arduins



In theory, this is easy. But in practice it turned out that arduina is not multitasking. That is, it cannot receive and send data at the same time, each process must be conducted separately. The way out was a timeout. The device waits for 7 minutes for the command to arrive and, if it hasn’t arrived, sends its data (the delay between “Mars” and “Earth” came in handy).

The device sends data in the following form:
1st line: / temperature from an analog temperature sensor / humidity / temperature from a digital thermometer
2nd line: / temperature from DHT11 / pressure / voltage supplied to the MC (microcontroller)

It can accept commands in the form of ASCII encoded bytes, which we enter into the terminal as letters (for example, the English "P" is accepted as 80). The list of teams was formed during development:

P - rotation of the panoramic camera.
D is the temperature read from the sensor inside the MK.
R - software reboot.
1 - open the protective cover (not used)
2 - close the protective cover (not used)

2. Camera

I figured out the main problem. Now the question is, which camera to use? A phone connected to a PC via Bluetooth / WiFi will drain very quickly. Therefore, I decided to use Presrigio's USB webcam.



Yes, she’s wired. However, telemetry was still broadcast on the radio, so I do not consider this a “scam”. The video was captured through Debut Video Capture.
The camera was mounted on a servo and could rotate 180 degrees to take panoramas.



3-4 - Sensors

Compared with the previous mission, this unit had a much larger number of sensors. True, in the end, the law “from the idea to the implementation of the functionality is reduced” has contributed - I found it unnecessary to tilt, gas and heat. The temperature sensor has been duplicated three times.

5. Housing A

cardboard box is in a sense convenient, but not serious. I'm not particularly friends with metal, but it’s more common to work with wood. Having decided on the sizes, I sawed out such a box from a piece of plywood





In it, I myself made holes for the camera drive and sensors.

6. Sleep mode

To save power, sleep mode has been entered. It was implemented like this: when little light fell on the photoresistor, the device stopped the program work (an empty cycle was scrolling). When there is enough light, the apparatus functioned.

In the photo, there is a photoresistor



7. Power

The device was powered by six Duracell Power Check finger batteries, giving a total of 9V.

I packaged this whole thing, tested it, and in the end it turned out like this:







Launch

Before the launch, the connection suddenly stopped working. Diagnostics showed that the problems lie in the digital thermometer. There was neither time nor the strength to dig into it, so I just cut it out like appendicitis. Also, I considered the protective cover that covered the sensors to be an unnecessary element, so I removed it too.
The guarantee of the device is 2 days (according to the previous mission). Work was scheduled for 5 days. The goal is to compile weather charts of Mars and take panoramas of the surface.
As soon as everything was settled, Explorer-2 hit the road - on the windowsill.

Flight timeline

Day 1 (04.17)

Explorer-2 successfully landed. First of all, the following data were obtained - ambient temperature 15C, temperature inside the case 20C, humidity 39% and atmospheric pressure 101619 Pa. The first frame was also shot from the surface of Mars:



A few minutes later the first panorama was taken (see higher resolution panorama here ): The



panorama was taken on the basis of the video captured from the camera at the time of movement.



Communication with the device was not always supported. I read the data in "sessions."
Somewhere at 8:40 p.m. a notification was sent to the terminal that Explorer had gone into sleep mode:



So the first working day ended. No problems have arisen, just surprisingly.

Day 2 (04/18)

The panorama of the last day was shot in the evening, now I wanted to do the morning. After reading the telemetry, I gave the command to take a panorama.

( Watch in higher resolution )


In general, everything worked so smoothly that it was even a little boring. Just come and take the data. I wanted some interesting situations. And they did not take long to wait.
All day I was recording evidence. At the end of the day, after the device



went into sleep mode, averaged and entered into the table: The day passed without failures. In theory, the next expiration of the operation guarantee of the device (Explorer-1 died after 2 days). Will the second version stretch? In any case, the battery charge did not decrease much during the day and there was no reason for concern.

Day 3 (04/19)

He began to read telemetry in the morning. A surprise was waiting for me - the voltage on the controller dropped by 0.5V. The analog sensor also began to increase temperature, which indicates a discharged (incomplete) battery. Sensors gave false evidence. To normalize them, I rebooted the device. After a few minutes, everything returned to normal. It became clear that energy should be saved. Therefore, I did not take panoramas and did not send any commands to the device. Just read the testimony.
After a couple of hours, the nov connected to the device. telemetry crawled, but then bam ... and broke off. Attempts to establish a connection failed. The device passed the dying lines:

/
89/49/22/101790/4417

Last picture:



And stopped. Forever and ever.
An autopsy showed that the batteries were dead.

Explorer-2 after completing the mission



It was insulting on the one hand and joyful on the other. It's a shame because there were plans for 5 days, I wanted to get more accurate data, to adapt to the panoramas.
The joy was that he worked out more than a guarantee (3.5 days). He worked much more stable than his predecessor. I managed to do what I wanted. All tasks were completed.

According to the results of Explorer - 2, the following graphs were obtained:

What next?

I have two ways:

1. Development of Explorer - 3
2. Construction of a simulator of the spacecraft cockpit

Path one. The
look of Explorer-3 is already looming for me. This time, the apparatus will be equipped with a drill for drilling the soil (the apparatus will be on the ground) and a spectrometer to analyze the chemical composition of the atmosphere and samples delivered through the drill. In fact, a spectrometer is not such a complicated thing. I’ve already acquired a diffraction grating, and then it’s a small matter - you need to make a chamber of homogeneous material and equip it, for example, with a lighter in order to burn samples and analyze the spectrum.
But, I give my preference to the second path.

Second way

Many people know that before flight astronauts train on a special simulator-copy of this apparatus. That is, a real flight is simulated. I chose the cabin of the American Mercury device as the optimal solution. It is single and uncomplicated in design; it also has a set of functions and a control panel device. I don’t know what will come out in the end, but at least a simulator of orbital flight should turn out. Shaking from engines, control panel, MCC, etc. will be played. I am already studying the details of the flights of the “Unions” in order to try to repeat the process as much as possible. The cabin itself will be a symbiosis - I’ll take something from Mercury, something from Soyuz. If everything goes smoothly, then docking with the ISS will be added, fortunately, this is at least difficult to implement, but real (in general, I will not fly into real space, so I will fly to mine).





Cabin construction begins in June. I hope that everything will be implemented.