(41) LED Resistor Picker
02-20-2017, 12:39 PM (This post was last modified: 02-20-2017 12:43 PM by damaltor.)
Post: #1
 damaltor Member Posts: 224 Joined: Dec 2015
(41) LED Resistor Picker
This program allows to pick a resistor for an LED. It uses the variables VCC (input voltage), U.F (forward voltage of the LED), R (resistor) and I (current through the LED) and can claculate any of the four after giving it the three others. It works similar to the TVM program of the advantage module: It uses USER mode and displays a menu which can be used like a softkey menu. Entering a number and pressing the corresponding key sets a variable to a value, and pressing a key without keying in a value before will calculate the selected variable. It is not the shortes possible program, but it works nicely and is easy to use.

Code:
VCC  |  R  |  +--U.F  | LED  | GND

Example 1: Finding a Resistor for a 2.2V LED with 5V input voltage and 20 mA
Code:
Input         Output XEQ LEDR      VCC  U.F R I (Menu, can be shown anytime by pressing J) 5 A           VCC=5.000 (Set input voltage to 5V) 2.2 C         U.F=2.200 (Set LED forward voltage to 2.2V) 0.02 E        I=0.020 (Set desired current to 20 mA) D             R=140.000 (perfect resistor value would be 140 Ohms) 150 D         R=150.000 (next standard resistor is 150 Ohms so we pick that) E             I=0.019 (Current would be 19 mA with the selected resistor, which is probably fine)

Example 2: Find maximum allowed input voltage for an optocoupler which has a forward voltage of 1.5V and a max. current of 10 mA if a resistor of 1000 Ohms is used. Is 12V as input voltage ok?
Code:
Input         Output XEQ LEDR      VCC  U.F R I (Menu, can be shown anytime by pressing J) 1.5 C         U.F=1.500 (set forward voltage to 1.5V) 0.01 E        I=0.010 (set current to 10 mA) 1 EEX 3 D     R=1,000.000 (set resistor to 1000 Ohms) A             VCC=11.500 (Maximum voltage) 12 A          VCC=12.000 (if we would like to use 12V as input....) D             R=1,050.000 (...the resistor should have been at least 1050 Ohms)

The program has 70 Steps in 20 registers and fits onto one magnetic card using both sides. It uses storage registers 01 to 04.
Code:
01 LBL "LEDR" 02 LBL J 03 SF 27 04 CF 22 05 "VCC  U.F R  I" 06 PROMPT 07 GTO J 08 LBL A 09 "VCC" 10 STO 01 11 FC?C 22 12 XEQ 11 13 GTO 99 14 LBL C 15 "U.F" 16 STO 02 17 FC?C 22 18 XEQ 22 19 GTO 99 20 LBL D 21 "R" 22 STO 03 23 FC?C 22 24 XEQ 33 25 GTO 99 26 LBL E 27 "I" 28 STO 04 29 FC?C 22 30 XEQ 44 31 GTO 99 32 LBL 11 33 RCL 03 34 RCL 04 35 * 36 RCL 02 37 + 38 STO 01 39 RTN 40 LBL 22 41 RCL 03 42 CHS 43 RCL 04 44 * 45 RCL 01 46 + 47 STO 02 48 RTN 49 LBL 33 50 RCL 01 51 RCL 02 52 - 53 RCL 04 54 / 55 STO 03 56 RTN 57 LBL 44 58 RCL 01 59 RCL 02 60 - 61 RCL 03 62 / 63 STO 04 64 RTN 65 LBL 99 66 ęś”"=" (append =) 67 ARCL X 68 PROMPT 69 GTO J 70 END
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