2013
09.19

fotw-ble-and-pulse-sensor

We think [Thomas Brittain] is onto something. We often post to our personal blogs so that we have a reference to how we did something. But he also keeps a long post that documents his abandoned projects. It ends up serving as a quick start if he ever decides to pick up the torch once again. Lucky for us he’s included his failures in the write up. This Fail of the Week features the top two posts on his Incomplete Works page. The first is an attempt to make his own pulse sensor. The second is a miserable experience with a cheap Bluetooth Low Energy module.

For the board on the left, [Thomas] managed to release some smoke from the components during the first test. As a learning experience he decided to recreate an open hardware pulse sensor. It is made up of an op-amp reading from a photo sensor, paired with an LED to light up the tip of your finger. He laid out his own board in Eagle and put in a $2 order with OSH Park. The image above shows [Thomas] reflowing the photo sensor using his clothes iron. After the rest of the assembly was complete he fired it up — producing the oft mentioned magic blue smoke. A second run on the board ended in folly also, perhaps because he reused components from the initial “smoked” board. One thing that this failure turned up was an interesting article on counterfeit parts.

We love reading about counterfeits so we’ll just drop a couple other links here to fake Arduinos and fake Apple PSUs.

The second fail is a Bluetooth Low Energy module that never showed the performance [Thomas] desired. He started off the project with the intent to use a TI CC2540 radio chip directly. But when he was elbow deep into modifying an example PCB for cheaper printing he decided to pivot. Without proper tools to troubleshoot the radio signal he figured it best to go with a module and just make his own breakout board. Above you can see the HM-10 module soldered to his breadboard friendly PCB (also from OSH Park). Those who have played with Bluetooth modules may already see this coming, but a chunk of his troubles were caused by the firmware running on the chip and a general lack of guidance on how to interact with the firmware’s features. Furthermore, level conversion was an issue. And when he did finally see some results from the device the effective range was just a few inches.

Bluetooth Low Energy is just starting to pop up in hobby electronics projects. We’d love to hear your own experiences — good or bad — with BLE hardware. Please leave a comment if you have a story to share.


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story – or sending in links to fail write ups you find in your Internet travels.

Filed under: Hackaday Columns
, Fail of the Week: Smoking pulse sensor and BLE dissappointment,
–Via Hack-A-Day