That's right.FvM said:IR absorption of water and many other liquids is good point. But I still think, that a lot of other issues are contradicting an industrial use. Without a problem specification, the discussion is more or less hypothetical.
Your teacher's quite right!fantabulous68 said:oh no!!!! my lecturer sd i must not use dat circuit i posted bt must get a new design to the same specifications...................!!!!what is this gal to do.
Im gna start from scratch like i neva saw that circuit b4, wen i come up with somethang useful il ask 4 guidance
I'm fraid that in the top posted Author design, any low photocurrent generated by PD forces OPAM-amplifier saturated with output voltage always 0V (Gnd). Interchanging PD Anode /Cathode connections may fix this mistake.FvM said:Saturation current is mainly a matter of load resistance.
FvM said:The shown circuit uses a remote control receiver IC. It's generally not suited for CW mode of operation. It's optimized for pulse signal transmission with a maximum base band pulse width. Also the receiver AGC doesn't allow to set a defined threshold.
Thanks for an idea.FvM said:I see options for circuit improvement in a different regard: A synchronous detector at the receiver can provide a better supression of AC light interferences.
fantabulous68 said:how can i modify the circuit to detect if the target is in a pre-defined range from the detector?
No, it's just fine as connected in the circuit.I'm fraid that in the top posted Author design, any low photocurrent generated by PD forces OPAM-amplifier saturated with output voltage always 0V (Gnd). Interchanging PD Anode /Cathode connections may fix this mistake.
Not yet! The receiver module TSOP1838 is designed for PCM communication.fantabulous68 said:thanx so much for the feedback all!!!mwah...
"Distance (level) alarming thresold can be set (tunned) if the LED current limit resistor (in trasmitter side) is replaced by a variable one."
the 2nd posted cct uses a variable resistor in the transmitter side.
MY Question:
Can i use the transmitter in the 2nd cct i posted
for my project???
Added after 7 minutes:
Oh yes! Sorry, there're 2 LEDs only. I have to replace my glasses.fantabulous68 said:***@fantabulous68
Normally, drop voltage for LED in forward current is about 1.6-1.7V. So 3 serial connected LED may require drop voltage more than the supply voltage (5V).***
sorry, im a bit confused. why do u mention 3 leds
Thanhlongbin??
No, FvMFvM said:No, it's just fine as connected in the circuit.I'm fraid that in the top posted Author design, any low photocurrent generated by PD forces OPAM-amplifier saturated with output voltage always 0V (Gnd). Interchanging PD Anode /Cathode connections may fix this mistake.
.
1. Your IR receiver has FOV (Field of View or angle of view) about 50-60 degree. If the tank is too tall, or its bottom is too small, the reveiver may be affected by reflected beam from the tank walls that causes a fault alarm. For this case, a circular black plastic tube can reduces the PD FOV.fantabulous68 said:1) any1 recommends the use of a circular barrier surrounding the led(transmitter side) for noise immunity?
Added after 1 minutes:
circular black plastic tube.
2) what functions/modules can the synchronous detector be broken down into?
I want to believe so much! But Google book says:FvM said:Believe it or not...
From a TI data sheet. Obviously a rail-to-rail OP is required.
Hi,fantabulous68 said:the design must:
indicate the liquid level in a container using infrared.
EG. if the container has 10cm height of liquid in it, THEN the design must display the level
" 10cm level"
**********************************************************************
the rest of the specifications:
The design should be useful in liquid level or proximity detection. It should operate by detecting the distance from the target by reflection of an infra-red beam. It should safely detect the level of a liquid in a tank without any contact with the liquid itself. The device's range should be variable, from a couple of cm. to about 50 cm.
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i will need to display the level, hence i have to use a microcontroller:lcd/2 7segment displays.
does any1 have a circuit and code which uses a pic microcontroller/stk500??
that would be useful in this project plz refer me to the links. thanks
FvM said:Perhaps other forum members, that also have built similar circuits can comfirm it's correct operation. I'm not sure, if you misunderstood photodiode or OP operation.
FvM said:As my last explanation attempt: As long as the OP cicrcuit is operating in linear range, the photodiode is zero rather than forward biased. The photo current flows from OP output through the conversion resistor into the cathode - the current polarity is the same as in reversed bias PD operation.
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