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#Post#: 119--------------------------------------------------
Re: LDR Connection
DIR By: geneveokevin
Date: August 16, 2016, 1:49 am
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LDR shows an analog voltage if you connect a voltmeter across
it. You need to interface an ADC with 8051 .
link-Interfacing ADC to 8051
First you should build an external LDR circuit for your
application. Then you simply need to connect the LDR across PIN
6 and 7 of the ADC. By doing this, the analog DC voltage across
LDR is converted to binary form. The binary value depends on the
resolution of ADC.
Then you need to program your 8051 ,using the data provided by
ADC, to suit you application.
#Post#: 126--------------------------------------------------
Re: LDR Connection
DIR By: meek-mic
Date: August 17, 2016, 12:08 am
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We connect the LDR to the Base. The role of the base region is
to function as the trigger for a larger emitter-to-collector
current. When the base current receives sufficient current, a
larger current then flows from the emitter to the collector.
When the base of the transistor receives sufficient current, the
charge carriers from the emitter are attracted to the holes in
the base region. This creates an avalanche effect in which the
current continues on to the collector region, which the large
current outputs through.
#Post#: 148--------------------------------------------------
Re: LDR Connection
DIR By: geneveokevin
Date: August 21, 2016, 12:42 am
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haha nabasa ko lang ma'am ... ;D
Light Dependent Resistors (LDR) are also called photoresistors.
They are made of high resistance semiconductor material. When
light hits the device, the photons give electrons energy. This
makes them jump into the conductive band and thereby conduct
electricity.
#Post#: 151--------------------------------------------------
Re: LDR Connection
DIR By: geneveokevin
Date: August 21, 2016, 1:04 am
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base ma'am
Transistors can be regarded as a type of switch, as can many
electronic components. They are used in a variety of circuits
and you will find that it is rare that a circuit built in a
school Technology Department does not contain at least one
transistor. They are central to electronics and there are two
main types; NPN and PNP. Most circuits tend to use NPN. There
are hundreds of transistors which work at different voltages but
all of them fall into these two categories.
Transistors are manufactured in different shapes but they have
three leads (legs).
The BASE - which is the lead responsible for activating the
transistor.
The COLLECTOR - which is the positive lead.
The EMITTER - which is the negative lead.
#Post#: 157--------------------------------------------------
Re: LDR Connection
DIR By: Dioni
Date: August 21, 2016, 11:50 pm
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--- Quote from: cefresto link ---
>
> The base of the transistor acts as the "gate" where the
electrical supply enters and the one who is the lead responsible
for activating the transistor. And because of that the LDR
should be connected to it.
>
> For example, we are using NPN transistor and we connected the
LDR to its base, when it’s light, the LDR has low resistance.
This makes the voltage at the base of the transistor higher.
High enough to turn the transistor ON. Because the transistor is
turned on, current flows through the transistor. It flows from
the positive battery terminal, through R1, the LED, and the
transistor down to the negative battery terminal. This makes the
LED light up. And when its dark, the oppposite happens.
HTML http://www.build-electronic-circuits.com/ldr-circuit-diagram/
>
> :)))
>
--- End Quote ---
You're correct it is connected in the BASE since the base acts
as a gate which enable electric supply to flow.
#Post#: 158--------------------------------------------------
Re: LDR Connection
DIR By: Dioni
Date: August 21, 2016, 11:58 pm
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--- Quote from: Junaimah link ---
>
> In creating our circuit the base part of the transistor are we
usually connect to the LDR. Because base part of the transistor
is the gate controller device for the larger elecrical supply.
By sending varying levels of current from the base, the amount
of current flowing through the gate from the collector may be
regulated.
>
--- End Quote ---
Thats right ! You're correct, the base part of the transistor
are usually connected to the LDR.
#Post#: 159--------------------------------------------------
Re: LDR Connection
DIR By: Dioni
Date: August 21, 2016, 11:59 pm
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--- Quote from: butihenmy link ---
>
> In creating a circuit the base part of the transistor is
connected to the LDR. Where the base of the transistor is act as
a gate gate controlle r device. This example is what i've read
on some sites. When it’s dark, the LDR has high resistance. This
makes the voltage at the base of the transistor too low to turn
the transistor ON. Therefore, no current will go from the
collector to the emitter of the transistor. All the current will
instead pass through the LDR and the potentiometer. When it’s
light, the LDR has low resistance. This makes the voltage at the
base of the transistor higher. High enough to turn the
transistor ON. Because the transistor is turned on, current
flows through the transistor. It flows from the positive battery
terminal, through R1, the LED, and the transistor down to the
negative battery terminal. :) :) :)
>
--- End Quote ---
You're correct it is connected in the base of the transistor.
:D :D
#Post#: 160--------------------------------------------------
Re: LDR Connection
DIR By: Dioni
Date: August 22, 2016, 12:00 am
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--- Quote from: cha sarmiento link ---
>
> Weusually connect the LDR to the base part of the transistor
because mostly in the way of constructing a circuit that turns
on the LED when it goes dark. In the LDR and the other Resistor
form a simple 'Potential Divider' circuit, where the centre
point of the Potential Divider is fed to the Base of the NPN
Transistor.
>
--- End Quote ---
That's right LDR is connected to the transistor's base
regardless if you use PNP or NPN transistor.
#Post#: 161--------------------------------------------------
Re: LDR Connection
DIR By: Dioni
Date: August 22, 2016, 12:02 am
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--- Quote from: darlyn link ---
>
> Mostly, we connect the LDR of the BASE part of the transistor.
>
--- End Quote ---
That's right you're correct! ;D ;D
#Post#: 162--------------------------------------------------
Re: LDR Connection
DIR By: Dioni
Date: August 22, 2016, 12:04 am
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--- Quote from: justine link ---
>
> We usually connect the LDR to the Base of the resistor.
> It is said that when the light level is low the resistance of
the LDR is high. This prevents current from flowing to the BASE
of the transistors. Consequently the LED does not light. ;D
>
--- End Quote ---
Thats right we usually connect the ldr to the base of the
transistor since this is where the current flow.
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