DaKandEKid
New Member
I'm made a simple circuit which i use to store the floor and section i parked my car in. It's a small circuit board which goes on my keychain that has two 7-segment LEDs, a pic uC and a 3V coin battery.
Since our Vdd is about 2.2V after the voltage drop from the SCR. The SCR is used to turn on the circuit after the power button has been pressed and stays on because the PIC draws enough current to stay above the SCR's holding current until we put the PIC to sleep. For more information on the SCR's purpose see the project website (see link below). We don't put any resistors to limit current to each of the display segments. This results in some characters which require less segments to illuminate to be brighter then characters which require more but this is okay by me.
The issue i'm having is all the seven segment displays we tried using were too dim until we tried Kingbright's APDC03-41CGKWA which has the following specs:
Chip Material: InGaAIP
Common: Cathode
Color: green (570nm)
Iv mcd: 4700 (min), 11000 (typical).
IV Characteristic: @2.1V If=20mA -> good luminous intensity
What i'm confused about is why do my other LED displays look so dim when the voltage being supplied to each matches the typical IV characteristic for the LED.
The PIC i'm using (16F628) can source and sink 200mA on portA and B.
Any thoughts?
For more information on the power circuit and other design decisions see my writeup of the project here:
**broken link removed**
Datasheet of known working display:
**broken link removed**
Schematic:
**broken link removed**
Since our Vdd is about 2.2V after the voltage drop from the SCR. The SCR is used to turn on the circuit after the power button has been pressed and stays on because the PIC draws enough current to stay above the SCR's holding current until we put the PIC to sleep. For more information on the SCR's purpose see the project website (see link below). We don't put any resistors to limit current to each of the display segments. This results in some characters which require less segments to illuminate to be brighter then characters which require more but this is okay by me.
The issue i'm having is all the seven segment displays we tried using were too dim until we tried Kingbright's APDC03-41CGKWA which has the following specs:
Chip Material: InGaAIP
Common: Cathode
Color: green (570nm)
Iv mcd: 4700 (min), 11000 (typical).
IV Characteristic: @2.1V If=20mA -> good luminous intensity
What i'm confused about is why do my other LED displays look so dim when the voltage being supplied to each matches the typical IV characteristic for the LED.
The PIC i'm using (16F628) can source and sink 200mA on portA and B.
Any thoughts?
For more information on the power circuit and other design decisions see my writeup of the project here:
**broken link removed**
Datasheet of known working display:
**broken link removed**
Schematic:
**broken link removed**