Ngā Tauira Pātai e Matapaki ana i ngā Diode Whakaputa-Mārama (LED)
Ko te tiode rama-whakaputa (LED) he taputapu haurua-ira e tuku ana i te mārama ina rere te iahiko hiko mā roto. Ko te āhuatanga kei muri i ngā LED e mōhiotia ana ko te electroluminescence, arā, ka tukuna te mārama e te rauemi haurua-ira ina whakaohokia e te iahiko hiko. Kua tino rongonui ngā LED i roto i ngā momo tono nā te mea he tino pai te mahi me te roa o te ora ki te whakataurite ki ngā pūtake mārama tuku iho pēnei i ngā pūangi incandescent.
I roto i tēnei tuhinga, ka matapakihia e mātou ētahi tauira raruraru e pā ana ki ngā rama LED, ka whakamāramahia hoki ngā otinga me ngā kōrero taipitopito hei āwhina i te mārama ki te ariā kei muri i tēnei āhuatanga.
Tauira Pātai 1: Ngā Āhuatanga Taketake o ngā LED
Pātai: Kei te LED te kaha ki te tuku mārama me te roangaru o te 650 nm (nanometer). Tātaihia te pūngao o ngā photon e tukuna ana e tēnei LED i roto i ngā irahiko-volts (eV).
Kōrero:
Ka taea te tatau i te pūngao photon mā te whakamahi i te whārite a Planck:
\[ E = \frac{hc}{\lambda} \]
kāore i te mana:
– Ko te pūngao photon te \( E \),
– Ko te pūmau a Planck te \( h \) (\(6.626 \times 10^{-34} \text{ Js}\)),
– Ko te tere o te mārama te (c) (3 x 10^8 m/s),
– Ko \( \lambda \) te roangaru o te mārama (650 nm, \(650 \times 10^{-9} \text{ m}\) rānei).
Mā te whakakapi i ēnei uara ki te whārite ka puta:
\[
E = \frac{6.626 \times 10^{-34} \times 3 \times 10^8}{650 \times 10^{-9}}
= \frac{1.9878 \times 10^{-25}}{650 \times 10^{-9}}
= 3.05 \times 10^{-19} \text{ J}
\]
Muri iho, ka hurihia e mātou ngā Joule ki ngā electron-volts mā te whakamahi i te huringa \(1 \text{ eV} = 1.602 \times 10^{-19} \text{ J}\):
\[
E = \frac{3.05 \times 10^{-19}}{1.602 \times 10^{-19}}
≈ 1.90 \text{ eV}
\]
Nō reira, ko te pūngao photon e tukuna ana e te LED he 650 nm te roangaru e tata ana ki te 1.90 eV.
Tauira 2: Ngaohiko Whakamua LED
Pātai: Ko te ngaohiko whakamua o te LED whero he 2V, ā, me 20 mA te iahiko hei whakahaere tika. Tātaihia te mana e pau ana i te LED.
Kōrero:
Hei tatau i te mana e mimitihia ana e te LED, ka whakamahia e mātou te whārite taketake mō te mana, arā:
\[ P = V \ngā I \]
kāore i te mana:
– Ko te mana i roto i ngā Watts (W) ko \( P \),
– Ko te ngaohiko i roto i ngā Volts (V) ko \( V),
– Ko te iahiko i roto i ngā Amperes (A) ko \( I \).
Whakakapia ēnei uara ki roto i te whārite:
\[
P = 2 \text{ V} \times 20 \text{ mA}
= 2 \text{ V} \times 0.02 \text{ A}
= 0.04 \text{ W}
\]
Nō reira, ko te mana e mimitihia ana e te rama LED whero e mahi ana i te ngaohiko whakamua o te 2V me te iahiko o te 20 mA ko 0.04 Watts.
Tauira 3: Te Whai Hua o te LED
Pātai: Ko te whai huatanga matū o te rama LED kikorangi he 30%. Mena he 0.1 W te mana hiko e whakamahia ana e te rama LED, e hia te nui o te mana e tukuna ana hei māramatanga?
Kōrero:
Ko te pai o te matū (η) te ōwehenga o te mana e tukuna ana i te āhua o te mārama (P_luminous) ki te tāuru mana hiko (P_input):
\[ η = \frac{P_{\text{luminous}}}{P_{\text{input}}} \]
Hei kimi i te \( P_{\text{luminous}} \), whakamahia te whārite e whai ake nei me te uara whai huatanga o te 30%, 0.30 rānei:
\[
0.30 = \frac{P_{\text{luminous}}}{0.1 \text{ W}}
\]
Pēnei:
\[
P_{\text{mārama}} = 0.30 \times 0.1 \text{ W}
= 0.03 \text{ W}
\]
Nō reira, ko te mana e tukuna ana e te rama LED i te ahua o te mārama he 0.03 Watt.
Tauira Raru 4: Ara iahiko LED raupapa
Pātai: E toru āu rama LED, he 2V te ngaohiko whakamua o ia rama, me hono raupapa. Mena ko te pūtake ngaohiko he 9V, whakatauhia te uara o te ātete e hiahiatia ana hei whakawhāiti i te iahiko ki te 20 mA.
Kōrero:
Ina honoa ngā LED i roto i te raupapa, ko te ngaohiko katoa e hiahiatia ana ko te tapeke o ngā ngaohiko whakamua o ia LED:
\[
V_{tapeke} = V_f1 + V_f2 + V_f3
= 2V + 2V + 2V
= 6V
\]
Ko te ngaohiko toenga me whakamarara e te ātete ko:
\[
V_{R} = V_{pūtake} – V_{tapeke}
= 9V – 6V
= 3V
\]
Ki te 20 mA te iahiko e hiahiatia ana, ka tatauhia te uara ātete mā te whakamahi i te Ture a Ohm:
\[
R = \frac{V_{R}}{I}
= \frac{3V}{20 \text{ mA}}
= \frac{3V}{0.02A}
= 150 \Omega
\]
Nō reira, ko te uara ātete e hiahiatia ana he 150 ohms.
Tauira 5: Ara Iahiko Whakawhāiti Auaha LED Whakarara
Pātai: I roto i tētahi ara iahiko, e rua ngā rama LED e whakarite ana kia whakarara, ko te ngaohiko whakamua o ia rama he 2V, ko te iahiko he 20 mA. He aha te iahiko katoa e hiahiatia ana mai i tētahi pūtake ngaohiko 5V mēnā he ātete te whakamahinga mō ia rama LED?
Kōrero:
Mō ngā rama LED e whakaritea ana kia whakarara, ka pāngia ia rama LED e te ngaohiko ōrite, arā, ko ō rātou ngaohiko whakamua, ā, nā te mea e hiahiatia ana he 20 mA o te iahiko mō ia rama LED, ko te iahiko katoa ko:
\[
I_{katoa} = I_1 + I_2
= 20 \text{ mA} + 20 \text{ mA}
= 40 mA
\]
Hei tatau i te uara ātete mō ia LED:
\[
V_{R} = V_{pūtake} – V_f
= 5V – 2V
= 3V
\]
Ko te uara ātete hei whakawhāiti i te iahiko i roto i ia LED ko:
\[
R = \frac{V_{R}}{I}
= \frac{3V}{20 \text{ mA}}
= \frac{3V}{0.02A}
= 150 \Omega
\]
Nō reira, me whai ātete 150 ohm ia LED. Ko te iahiko katoa e hiahiatia ana mai i te pūtake hiko 5V he 40 mA.
Whakamutunga
He wāhanga nui ngā rama LED i roto i ngā hikohiko hou nā te mea ka taea e rātou te whakarato rama tino whai hua me te roa o te ora. Mā te mārama ki ngā ariā taketake pēnei i te ngaohiko whakamua, te iahiko, te mana, te whai huatanga matū, me te whirihora i a rātou i roto i te ara iahiko ka whakaratohia he turanga pakari mō ngā tono mahi. Ko ngā tauira i runga ake nei he taahiraa tuatahi ki te matatau ki ngā tono me ngā tataunga e pā ana ki te whakamahinga o ngā rama LED i roto i ngā ara iahiko hiko.
