Ordered an arduino starter kit from aliexpress Link

The parts list they provide (as a jpg on the order page) is vague and not very descriptive, I've gone through most of the parts and am down to three they did not list.

  1. Capacitor? -- Looks to be a capacitor, labeled HDX and nothing else, rattles when I shake it. Unknown part #1 - HDX capacitor?
  2. Black LED -- I think this is a flame sensor; if it is, what's the difference between this and an infrared receiver (like a 1838B) or photoresistor? Unknown part #2 - flame sensor LED?
  3. They also list something as 'a digital control' near the bottom of the list, not sure what that is? Every other part from the list is matched up and I don't see anything different in the first picture (not parts list picture) from what I have received in the order.
  • Rather than linking to OneDrive you can press the image button, browse to the image on your PC and it will automatically put it on imgur. Stack Exchange back those up so the image won't go missing in the future.
    – PeterJ
    Commented Dec 30, 2014 at 6:19
  • Thanks for the tip; didn't know that. I took the picture as I was typing my question and didn't want to go download them. I'll upload them here now.
    – PGT
    Commented Dec 30, 2014 at 6:24
  • The "black LED" is not a LED. I forget what exactly it is, but I have one sitting in my parts box. I'm pretty sure it is a photo-something. Light waves affect it. As for the capacitor-looking things that rattle, I got no idea. Commented Dec 30, 2014 at 7:31

3 Answers 3

  1. Those are tilt sensors. The rattling is a metal ball that contacts two pins inside, closing the connection.

  2. The 1838B is a full module that partially decodes the received IR so that a MCU can fully decode the rest easily. What you have there is a bare phototransistor with an IR window on the top. You would use it for proximity or presence sensing. Instead of varying its resistance, it varies the amount of current it will pass.

  3. Probably the single-digit 7-segment display, as opposed to the 4-digit display they have listed as "4 digital tube".

  • Just did some tests with the parts and this answer is correct: #1 is a vibration sensor, it points up and cuts off current if it detects vibration. #2 is a phototransistor, works with flame but not light (unsure how this works in comparison to photoresistor, will have to do some research). For #3, I am leaning towards them meaning the single-digit 7-segment display, since there isn't anything else on the parts list that matches it, but unsure why they used 'control', I think maybe they just translated wrong or the vendor doesn't really understand what the component is.
    – PGT
    Commented Dec 30, 2014 at 7:44
  • @PGT: Flames give off much more IR than a light bulb. Commented Dec 30, 2014 at 8:07
  • Just a quick thanks. I ordered a set from a supplier called Sintron, also had some vague descriptions and the 2 listed above are the two I was also having difficulties with. At first I thought caps, but...they shouldn't rattle... :D
    – null
    Commented Apr 12, 2015 at 13:50

I recently purchased the arduinotech module learning Kit and contains both components shown above. It does mention an Infrared Photo Diode which it think is your "Black LED".

Thanks for the heads up on the HDX switches. Now I know what they are.:)


The HDX is a "Tilt Switch" Turns on/off depending on the angle.

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