Need help with a project? Trying to find a component? Post any general technical questions here.
-
thesfxstudios
- Posts: 1
- Joined: Tue Apr 01, 2014 8:30 am
Post
by thesfxstudios » Tue Apr 01, 2014 8:45 am
Dear all tech people
i am trying to build a driver blinking detection system with the aid of infrared. i have come up with a idea of a block diagram for this and my circuit has no software involved. the infrared emitter emits low light infrared towards the eye and the detector detects the length of the blink before the driver goes into micro sleep. so if the person blink is longer than 2.1 seconds the alarm should go off. i am having difficulty with the actual circuit design and how to gain values as i am not an electronic or electrical engineering student but if any of you guys can help me with this i would be very very grateful. i have attached the block diagram. please correct me if im wrong and hope it helps!
thank you
Sam
- Block diagram
- block diagram.jpg (69.45 KiB) Viewed 2814 times
-
Pauldf
- Posts: 170
- Joined: Mon Jun 10, 2013 7:42 pm
Post
by Pauldf » Tue Apr 01, 2014 4:03 pm
You can probably use something simple like a 555 astable to drive the emitter.
The systems I have come across have the detector driving the base of an NPN transistor to amplify the pulse.
The pulse then goes into a series capacitor which will block DC. I think a diode is also needed in series. The result is fed into a capacitor (connected between it and 0v) which charges when a pulse is seen.
The result is fed into an op amp +ve leg with the trip level set on the -ve leg.
A variable resistor across the 2nd capacitor will determine the length of time it takes to discharge.
I'll have to wait a week or so to see if I can find a diagram as I am on my week off.
