I have collected some questions I got from you with answers here about DIY sensors. If you have any questions outside these don’t hesitate to use the contact-page here.
Q: What do I need to get started on DIY-sensors?
A: You do need some stuff. Common stuff to all DIY-sensors are:
- Arduino Pro Mini 3.3V 8MHz or 5V 16MHz – Look into sensors parts list
- A servo-wire from Arduino to receiver
- Depending on building instructions a sensor module
- Depending on building instructions some resistors and other compnents
- Depending on building instructions some wire between sensor-module and arduino
- Programmer for Arduino
I also very highly recommend you to get a Jetibox. The Jetibox Mini is really helpful to set the sensor settings and make some communication test’s!
As the programming cable the cheap USB to TTL adapter have done a great job for me. Search in Ebay for “USB to TTL Arduino” and you’ll get a ton of choices, here’s a example:
Wiring of programmer to Arduino is as follows:
Cable Black <-> Arduino GND
Cable Red <-> Arduino VCC
Cable Green <-> Arduino RX
Cable White <-> Arduino Tx
I usually do not solder any pins to Arduino, instead I have 4 pins in the cable and simply put them into Arduino programming holes and apply some pressure while uploading. Makes a neater end result.
Q: How to know if Arduino is 3.3V or 5V, nothing is marked?
A: This is sometimes an issue, Chinese manufacturers rarely mark the version on the PCB even if there is checkboxes available on the back of PCB. But this is easy, power up the Arduino with nothing connected and measure between VCC and GND, answer is right there.
Q: How to program the sensors?
A: First, watch the tutorial:
Hopefully that would do the trick. If not you might need to look below for hardware-issues.
Q: My programmer does not work?
A: Check windows Device Manager, if you have driver-issue follow this guide. Pretty much all cheap China-programmers are done with fake Prolific chips. The guide above helps you on that.
Q: I cannot program the Arduino?
A: If you are using Arduino IDE then look into error-messages. Press CTRL+R to build the sketch, if you get the information like this in the end:
you’re good to go. If transferring to your Arduino-board does not work you most likely have issues with your USB-TTL adapter, you haven’t chosen right board and/or serial port in your IDE settings or you simply have TX/RX cables wrong way.
For my own RCT Firmware Uploader have a look on the dedicated page here.
If you are using XLoader-method you most likely did not press the boards reset-button in exactly right moment. Itä takes a few practice-runs to learn it. While not being perfect with progress-information XLoader is still easiest way to program the sensor.
There’s more comprehensive guides inside the RFID-Sensor page.
Q: How reliable are the values?
A: DIY-sensors on these pages can be off with very small difference but it depends on the actual sensor module and programming. Cheap Ebay-stuff might have very small offset in some cases. Testing have proven that if there is a difference it’s so small it has no importance. Accuracy also has to do with what we are measuring, for example Fuel Sensor uses the exact same flow-module Jetimodel uses and since it counts flow with pulses the accuracy is exactly the same, my AmpSensor uses the same measuring IC (ACS758) as Jetimodels MUI. One question tho, does it have a difference if cylinder temperature is 88° C or 89° C or if rpm is 7820 r/min or 7830 r/min?
As an example, here’s Jetimodel’s MVario2 and DIY Jeti AltMeter (new version Jeti VarioMeter) compared in same flight:
And when zooming into details:
We can conclude that accuracy is like amount of horsepower’s in Rolls Royce cars, “enough” :)
Q: What’s the life-span on DIY-sensors?
A: DIY-sensors will most likely outlive your model. Key things are your soldering-skills, choice of components and correct assembly so they will tolerate some vibrations for example. One thing we do have to remember, cheap Ebay-stuff from China is often either counterfeit or relabeled used chips. One curiosity also, Atmega328 in Arduino’s do not like too much EEPROM-writing, that is why my sensors do not do any memory-writing in working loop, only when storing settings. (And you don’t do that 10000 times…)
Q: Your Ebay-link is dead, can I use <insert link here> instead?
A: If it looks exactly the same then most likely yes. Look for connection-type (connections with same pin-names) or same chip-type. For example Jeti Dual HightTemp uses MAX6675, RFID-Sensor uses RC522-board with SPI-interface, GPS-Sensor uses NEO-6M or NEO-8M (Preferred for accuracy) module with serial interface etc etc. I would of course like very much if you would notify me of dead links!
Q: Why would I buy expensive Jetimodel’s sensors when I can make them for a small cost myself?
A: In some cases this migh be true. It is a question only you can answer for your part. Like with anything you build yourself you need to trust your own skills. Put that in relation to what you are measuring and how you use the telemetry-value. If you make a sloppy build of (for example) Fuel-sensor and it starts a leak with a crash in result, what’s the reliability?
Also one thing we have to remember, Jetimodel’s telemetry-protocol is not fully open, there are functions that cannot be done with DIY-sensors for example Device Explorer integrations. Most often these can be done via Jetibox so in some cases difference is not that big. The choice of the actual measurement component is also a factor, Jetimodel uses what is best suited while DIY-sensor uses what what is best suited but also very affordable. And very often cheaper price is little bit visible in either function or accuracy.
As an example, Jetimodel’s MVario2 is ~85 euros, DIY Jeti VarioMeter is around 5 euro. DIY-sensor is not F5J approved and has no Device Explorer integration. Altitude-measuring performance is on par, vario-measurement is very close. DIY-sensor can be changed, calibrated, Jeti manufactured cannot. It all comes really to what you want.
Q: I cannot access sensor’s Jetibox!
A: When in Jetibox, go right to “<– MX –>” and press DOWN. Many of you press right and that’s wrong. Press DOWN. This happens quite often to people. I really would like to say RTFM but I won’t since I’m a nice guy :)
A2: Use Jetibox Mini!
Q: Can you do <insert sensor here> as DIY?
A: Most likely! If the measurement module can be connected to Arduino then it’s possible. We have to remember that the simplicity is one one demand I have. If it requires thirty wires, purpose-made PCB etc then it’s most likely not a “affordable DIY-sensor” anymore.
Q: I have a lot sensors, I need an Expander!
A: I have been looking into making a Expander. It has some programming-issues my skills are not up with. Making a 4-channel Expander would require 4 to 5 software serial ports and 4 of them needs to have Tx and Rx on same pin. That goes above my head at the moment but we’ll see what happens. My “DIY-philosophy” is “Affordable and easy” so there is a limit on hardware choices. But you have two options, get a Expander from shop or look into OpenXsensor here.
Q: Can I modify your code and share/sell the sensor?
A: Yes you can! At the moment all my DIY-sensors are shared in MIT-license. This combined with Arduino’s license means that as long as you use a unmodified Arduino-board you do not even need to share the code of the sensor you sell. You are required to include the MIT-license to your product tho. If you make a sensor with custom PCB including Arduino-design then all source (including PCB-drawings) needs to be shared too. Propriety is only possible with a sensor including complete arduino-board. You need to have a look on sensor-modules licenses too before doing anything. If you are making a product with my complete code or largely based on my code then a copyright-notice of origin needs to be included in your release.
I have seen some examples of situations recently where I find my code copied to 90-100% with another name. That is not in the spirit of open-source and is not acceptable.
In more detail about how to share your versions please read THIS.
Q: But, but why?
A: One reason. It’s fun to make something for yourself and see it in action. You should try it :)
RFID-Sensors in bulk…