We’d never developed a device before and with Simplexity’s guidance it didn’t seem hard. They designed our new LOOP CPR Controller to meet our requirements and work in the simplest possible way. With Simplexity, they don’t say simplification, it’s organic. It’s how they think. The result is exactly the new tool we need to train more students all over the world and save more lives with better CPR.
— Frank Powers,
Chief Technology Officer, Health and Safety Institute
With any mechanical design, reducing the number of moving parts reduces the number of failure points. Making the simplest mechanical design means keeping part count low, and designing the parts correctly for the manufacturing process. The LOOP has only three custom parts, the rest are off-the-shelf components.
In addition, by molding the LOOP housing out of translucent plastic the colored LEDs used for CPR performance feedback could simply shine through the housing without needing special mounting.
Simplexity designed all of the custom parts in SolidWorks® 3D CAD, and selected all of the off-the-self components and fasteners.
The electrical design focused on keeping things simple too. The system is powered by the USB connection; no batteries required. The system “smarts” are provided by a simple micro-switch, a 3-axis accelerometer/gyroscope combo, and an inexpensive microprocessor that manages reading sensor data, turning LEDs on and off, and sending data to the host PC. This allowed for a small, low cost circuit board
Besides the electrical engineering design, Simplexity managed the selection of suppliers and the process of getting from engineering prototype to final manufacturing release.
When it comes to developing efficient product code, the key is to do the right things in the right places. Embedded firmware takes more time to develop than PC software, so only critical functions are performed on the LOOP’s microprocessor. The firmware reads the sensors, does some basic data filtering, then packages the data up and sends it to the host PC over the USB cable. The firmware lights up the LEDs based on simple commands from the PC.
The software is split into layers to simplify and enable parallel development. The Simplexity team wrote the PC software to read data from the USB connection and convert the sensor to CPR data. This data is then passed to HSI’s software to collect it into the CPR training database and display it to the user. By properly partitioning the software architecture, Simplexity and HSI were able to develop in parallel.
Turning simple sensor readings into CPR data requires a set of sophisticated signal processing algorithms. Utilizing state-of-the art tools such as Matlab®, Simplexity developed custom software to convert low cost cell phone sensor data into CPR training data. This software utilizes advanced algorithms including the Extended Kalman filter.
Prototypes of the LOOP were built throughout the various stages of the product. For housing parts, machining was chosen over 3D Printing or other rapid prototype methods since the material had to be durable to withstand all the compressions during early life testing. The elastomeric cover was created using rapid prototype methods, by printing a positive that was used to make an inexpensive silicone mold and then casting the covers out of an elastomeric material.
To prove the design is robust enough for use in day-to-day training, Simplexity designed and built a compression life tester, affectionately known as the “Puckinator” since LOOPs were at first called "pucks". This device was built to perform compressions day in and day out, around the clock. While doing the compressions, Puckinator software checked every compression to make sure the LOOP measured the correct depth. The prototype LOOP was tested to one million compressions to verify that the design was robust enough to stand up to the toughest CPR trainees.
The LOOP is low cost, easy-to-use, and available worldwide. A wider adoption of quantitative CPR training means better trained first responders and, of course, better emergency response outcomes. Learn more about The LOOP at their website