G
Gman
- Jan 1, 1970
- 0
Hi there,
Thanks for the help on the test button question. Got another
non-electronics technician problem.
I am still working on this Sensor Circuit with LED indicators. The box
I'm building, I want it to be able to be used on either system voltage
of 14Vdc or 28Vdc with a spdt switch setting the box for the
appropriate voltage.
So I have eight sensors, eight LEDs (some with different ratings, see
below), two voltages and two states of DAYTIME (Bright) and NIGHTTIME
(Dim).
The LEDs are supplied directly by the sensors. This means that each LED
has it's own power supply so speak. But, all supplies will either be
14Vdc at one time, or 28Vdc at one time (you will not have both
voltages at the same time).
Because of the different LED colors I have to deal with a 2V and a 3V
LED at the two voltages of 14Vdc and 28Vdc, so my resistances are 550,
600, 1.25K and 1.3K at 20mA.
Its easy enough just to put a 600 ohm R inline with each LED, but how
do I switch so that ALL LEDs have a 1.3K R in front of them without
running all the power through my voltage selector switch (which would
defeat the purpose of using the power from the sensors and having an
indicator light up when power is supplied by the sensor)?
My next problem will be to DIM all the LEDs for the NIGHTTIME setting,
yet a third resistive value????
I'm trying to use more passive components rather than ICs and trying to
keep it simple as possible all the way, any suggestions are hugely
appreciated.
Thanks in advance.
Gman
Thanks for the help on the test button question. Got another
non-electronics technician problem.
I am still working on this Sensor Circuit with LED indicators. The box
I'm building, I want it to be able to be used on either system voltage
of 14Vdc or 28Vdc with a spdt switch setting the box for the
appropriate voltage.
So I have eight sensors, eight LEDs (some with different ratings, see
below), two voltages and two states of DAYTIME (Bright) and NIGHTTIME
(Dim).
The LEDs are supplied directly by the sensors. This means that each LED
has it's own power supply so speak. But, all supplies will either be
14Vdc at one time, or 28Vdc at one time (you will not have both
voltages at the same time).
Because of the different LED colors I have to deal with a 2V and a 3V
LED at the two voltages of 14Vdc and 28Vdc, so my resistances are 550,
600, 1.25K and 1.3K at 20mA.
Its easy enough just to put a 600 ohm R inline with each LED, but how
do I switch so that ALL LEDs have a 1.3K R in front of them without
running all the power through my voltage selector switch (which would
defeat the purpose of using the power from the sensors and having an
indicator light up when power is supplied by the sensor)?
My next problem will be to DIM all the LEDs for the NIGHTTIME setting,
yet a third resistive value????
I'm trying to use more passive components rather than ICs and trying to
keep it simple as possible all the way, any suggestions are hugely
appreciated.
Thanks in advance.
Gman