Child Fall Detection - Page 1
Forum section: electronics / projects

author: jagjeet k
author_rank: Newbie
timestamp: October 30, 2014, 10:58:22 am
content: I have constructed a circuit based on the above idea, and I am using a MMA7341 accelerometer, but the moment I connect the accelerometer to the circuit seem to be getting a high frequency noise on the 3.3V power. I have only one acceleremoter and cant try with another, but if I power the acceremeter seperately I dont see any noise. Kind of annoying...is there something more I can try out to check where the noise is comming from?http://www.ingenstech.com/projects/child-fall-detection/

author: tggzzz
author_rank: Super Contributor
timestamp: October 30, 2014, 11:23:11 am
content: Quote from: jagjeet k on October 30, 2014, 10:58:22 amDetails please, unless you want mostly irrelevant responses: full schematic, mechanical construction, frequency/amplitude, PSU decoupling and PSU connection (both cases), what happens when you touch your finger to different parts of the circuit.And most importantly: what have you tried doing and what was the effect.

author: Fred27
author_rank: Unknown
timestamp: October 30, 2014, 11:58:10 am
content: What's wrong with the in-built alarm? It starts slowly but rapidly builds up to a clearly audible level. Silencing it can be tricky though.

author: Wilksey
author_rank: Super Contributor
timestamp: October 30, 2014, 01:04:45 pm
content: Please excuse my ignorance, but what is the purpose of this?Are you attempting to send a SMS or something to a phone when the accelerometer detects a sudden change in one axis?When you have introduced the accelerometer is the only other thing attached the PIC?Why do you have a 5V supply just to seemingly power a LED?Have you checked that the LM317 current capability will allow you to drive a GSM module? Take note of the peak current at transmission burst (nominally 1.6-2A)Speaking of which what is the current capability of your regulator and is it man enough to supply the components?Maybe add some inductance (Esp if running a GSM engine) to the power supply.You probably don't need that 0.1u at the output of the 317.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: October 31, 2014, 04:55:10 pm
content: Children have built-in fall detection...

author: calexanian
author_rank: Super Contributor
timestamp: October 31, 2014, 07:04:16 pm
content: Does it just directly call child protective services for you and get a court order while it is at it? The little fall detector on the front of thier face has worked well for many millennia.

author: 0xPIT
author_rank: Regular Contributor
timestamp: November 01, 2014, 07:34:49 pm
content: FYI, MPU6050 devices have drop detection built in with programable thresholds.I simply wait for a fall (zero-gravity) an then expect a second or so when the sensor does not move, tried that on my granny and it works well in filtering out regular movement.Of course, this will not work if child falls and then rolls down a hillThere are a lot of scientific papers on that subject, there is no really accurate solution.

author: jagjeet k
author_rank: Newbie
timestamp: November 03, 2014, 11:52:32 am
content: Quote from: tggzzz on October 30, 2014, 11:23:11 amI see that... anyways I figured out the problem, it was a small strand of wire that was accidently and randomly sorting parts of the circuit. Cleaned the whole board with IPA and it was okay thereafter...thanks.

author: jagjeet k
author_rank: Newbie
timestamp: November 03, 2014, 11:53:43 am
content: Quote from: 0xPIT on November 01, 2014, 07:34:49 pmwill check it out thanks

author: jagjeet k
author_rank: Newbie
timestamp: November 03, 2014, 11:56:03 am
content: Quote from: Wilksey on October 30, 2014, 01:04:45 pmAll valid observations and yes the LM317 can power a GSM modem, it works fine... however I must have mentioned that I am not following the schematic in that drawing 100%... that was there to share the concept... my bad. Thanks anyways.