Please am working on a project which is to design an intruder alarm system using tsop 1738 ir sensor and tsal 6200 ir diode. But the problem am having is how to produce an electric signal of 38kHz and also how to make it constant irrespective of change in temperature so that it can always be detected by the ir sensor. Expecting your kind contributions thanks.:lol:
@eva4good< I am sure you can get your intruder alarm to work, but it is important to learn why design is done and the reasons should be made clear. Then you can never fail, unless you forget an assumption or cannot solve it in time.
Specs are based on Time. Budget, Performance, Environmental Specs etc.
You would do better if you tried to look at existing products and then try to reverse engineer them and make it better for your needs.
At least make a spec to indicate what exactly you plan to make.
Of course Make or Buy is a decision made in every stage of design. We can use this analog at every level from Systems down to silicon dust.
It is critical that you write yourself ( share it too)" a simple one page SPEC " like any commercial product brochure, and say what it wil do in a list of
measureable numbers and what environment it will work.
Otherwise you are wasting your time playing with parts .
1. Consider what can be detected by intruder motion; and then decide if it meets your criteria above in your spec.
- audible noise above ambient ( omni directional but poor s/n ratio detecting what sound an intruder makes )
- reflected light change ( can be wide angle or very narrow beam depends on distance and light ingress, careful design needed)
- transmitted light interrupted ( drop in can be multiple very narrow beams and detectors )
- reflected RF signal using return loss bridge and 1/4 wave wire, splitter and HC diode ( detects 5 m easily at low power)
- inexpensive Webcam GO or newer with motion sense software or equiv.
- ultrasonic reflection
Keep in mind SNR has a direct relation to error rate in
detection of anything. Stock market, intruders, cell phones (SNR=Signal to Noise Ratio) This is defined by Shannon's Law.
Next make a list of all noise sources relevant to your purpose..
Solutions are trivial after the problems are clearly defined. The challenge is to research what you need to solve with acceptance and rejection criteria and what technology can offer in each requirement then becomes easier. This, is Engineering.
The traditional outdoor sensor lights use IR diode like those in Remote controls for TV and the IR LEDs are powered from the AC power. typ ~20~50mA or IR light. A high value resistor biases a photo diode usually detects refected light changes as an ac signal then rectifies that. Usually as increase in reflected light since it is omnidirectional. It must be very low current integrated for a second or so to detect from afar. But it is adaptive so it is looking the noise of IR reflected from an otherwise static reflection off the ground. It works but can often be too sensitive and false triggered.
Now describe to yourself how yours will work and summarize that into your spec.
I could suggest a cheap transceiver Opto pair that would do everything for some ranges, but I want you to defined that range, sensitivity for size and accuracy