Why doesn’t your sensors cost 10€?

Why this post?

After I started making my own stuff (LogicSwitch, RFID-Sensor, WarmTX) for sale I have occasionally gotten emails saying they are expensive. This week i got one surprisingly aggressive email where a reader stated I’m ripping people off with my RFID-Sensor.

So let’s go through the process of how my RFID-Sensor comes for sale.

Step 1 – Design

Before anything the sensor has to be designed. As always it starts from an idea. The idea was to make a RFID-Sensor and AlastairC had made one earlier that was a great starting point. Since Lua is now available I wanted more functions of it.

Before anything can happen I had to search interwebs for suitable parts and order them. After they arrived started the sensor firmware programming. I can only assume how much time I have put to that but an assessment of around 70-80 hours is not far away. After all, I’m not a programmer.

Also, the sensor I’m selling is assembled with a middle-PCB, not with wires like the open-source i have posted. That is my own design, that means I had to draw the PCB with PCB-design software and order them. Add another 10 hours or so. Once again, I’m not a PCB-designer, things like that does not go fast for me.

Step 2 – Get materials

In order to get a solid product I can sell I need some basic stuff. That means I had to design and order the label to put on sensor. Also I ordered suitable heat-shrink. Also the Arduino’s, RFID-Boards and receiver wires do not travel to me without ordering.

User guide that is shipped with RFID-Sensor took about two hours in making, printing and folding a bunch of them took very little time.

Step 3 – Manufacturing

Everything I do I do by hand, no assembly lines available here. So this is how RFID-Sensor is made:

  • Test-program the Arduino-board to make sure it works before assembly
  • Test-use the RFID-board to make sure it works before assembly
  • Take the wire to receiver, strip the end and pre-solder them
  • Solder the wire to middle-PCB
  • Cut a strip of pin-headers to suitable pieces
  • Solder them to middle-PCB. That’s 26 solder points
  • Put the RFID-board to assembly
  • Cut the 9 pin-headers to fit
  • Solder the RFID-boards 9 solder points
  • Put the Arduino to assembly
  • Cut the 17 pin-headers to fit
  • Solder the Arduino’s 17 solder points
  • Test the sensor with receiver and transmitter
  • Cut a piece of heat-shrink, put it on sensor
  • Put the label on sensor
  • Put the sensor in anti-static bag ready for shipping.

Step 4 – Prepare to sell

The sensor was photographed, description was made, it was put to shop inventory and posted to shop. That only part of it. It also had to be put into my invoicing software and accounting software. (Not able to run any expensive software where everything is in one)

Step 5 – Customer buys one

Wohoo! Now I have sold one! So, let’s ship it!

  • Create a new customer to invoicing software by copying buyers name, address etc in there
  • Create an invoice with that information and the product & desired shipping method customer chose
  • Print the receipt, one for customer and one for my accounting books
  • Take the receipt and sensor, get a user guide and put them in a package
  • Go to shipping company’s website and fill in all the recipients information
  • Pay the shipping
  • Print shipping receipt for accounting books
  • Fill the accounting software with receipt information (2 receipts per transaction)
  • Print shipping documents
  • If outside EU fill in custom forms
  • Put everything on top of package
  • Put some RC-Thoughts stickers inside package
  • Seal the package
  • Mark the order as complete in shop
  • Email the tracking number to customer (If not done from any software)
  • Drive to post-office with the package


Kinda makes me sad that I felt the need to make this post. But it is apparent that there is people out there who do not understand the concept of “small batch manufacturing” and hand labor.

Price could be dropped if I would sell them by thousand and have them for example pre-assembled in China or something. But the minimum order in pre-assembly is way too high for me in order to make it possible. I do not have the resources to order 1000 units at one time. Simple as that. I do this for the love of hobby and some coffee-money.

I counted what I make from selling RFID-Sensor. I came to a whopping number of something like 1.50 to 2€ per hour. That’s before tax. Minimum wage in Finland is at the moment around 8.12€ per hour.

Still think they are expensive? You can always make your own, the how-to is available :)


8 thoughts on “Why doesn’t your sensors cost 10€?

  1. If the guy finds it too expensive, he has to remove his fingers from the ass and build it :-)

  2. Tero
    Define expensive, couple circuit boards bit of wire and some solder, then factor in time, development, experience, and just the pure ability to make it all work

    If anything they are to cheap so don't worry about the odd person who is negative just ignore


  3. You have nothing to justify!
    Just keep going on, thank you for keeping up with the excellent work on your page!

  4. Having assembled a couple, I'm certainly aware that they take time and concentration to do. I can only thank Tero for all the effort he's put into the project and for making it so freely available – and answering my stupid questions quickly and at all hours!

    If someone wants to save the effort and buy one off the shelf then why shouldn't you ask for something to reflect your work – buying an assembled one isn't compulsory after all! I suspect there are plenty of people who feel the same way – just ignore anyone petty enough to send you such messages.

  5. Tero, consider an app like Shopify or WooCommerce to simplify the order management process for you…

    1. I have WooCommerce. It helps but there's still the shipping, accounting and billing in separate places. Amount of transactions is not that big so it ain't that bad, just takes it's time :)

  6. Tero,

    don't worry about these persons. Why don't they make it the DIY way? They can't and want have done it by you but they don't want to pay for it. I don't want to make one myself, so I've ordered one. When it came to shipping I wodered at first, because some shops ship for ridicolous fee around half of the world. Sometimes it's less than shipping inside my country (Germany). But if I remember right in the scandinavian countries there a most things more expensive then in the rest of europe.

    Actually I'm waiting on my sensor, which is on the way somewhere between Finnland and Germany.

    1. Shipping in Finland is a total rip-off, basically monopoly on one company and thay just raise there fees all the time. maybe I need to move to China… :)

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