Where LED_ON is connected directly an Arduino digital pin.
The problem I'm facing is:
When LED_ON is LOW, the LCD is fully on (backlight and text), but when LED_ON is HIGH, the backlight doesn't fully turn off, but stay dim.
When I measure the collector's voltage in off state, it's around 3V, when it should be around 0V.
I tried changing the 1kR resistor to 10kR and 470R, but without success.
You are also turning off the LCD as well as the back light. This means that the inputs to the LCD are parasically powering your display. So when you turn off the LCD you have to make all the Arduino’s output pins connected to the display into input pins to prevent this.
I also think you need to include the 5V of the contrast pot into the switching circuit.
Grumpy_Mike:
You are also turning off the LCD as well as the back light. This means that the inputs to the LCD are parasically powering your display. So when you turn off the LCD you have to make all the Arduino’s output pins connected to the display into input pins to prevent this.
I also think you need to include the 5V of the contrast pot into the switching circuit.
I wouldn't expect the pins to power the LCD! :o
I placed all the data pins to INPUT and the LCD correctly turned off.
giova014:
I wouldn't expect the pins to power the LCD! :o
Then you should learn to! A circuit doesn't go away when the power is removed, its starts
taking power from whatever sources are available (for CMOS logic via the protection diodes
mainly)
You need to remove any signals driving a module before powering it down.
MarkT:
Then you should learn to! A circuit doesn't go away when the power is removed, its starts
taking power from whatever sources are available (for CMOS logic via the protection diodes
mainly)
You need to remove any signals driving a module before powering it down.
I thought the Backlight VCC and the Logic VCC were independent.
TomGeorge:
Hi,Didn't you built a prototype before going to PCB manufacture?
Tom.... :o :o :o :o
I was confident that it wouldn't be a problem and I couldn't afford the cost for prototypes, as it is almost a personal project with low quantities.
Normally, with bigger and serious projects I would build a prototype.
Grumpy_Mike:
Yes it would, use a scalpel, to cut tracks, an mod wire to make changes. Mod wire is wire used normally for wire wrap, it is solid but about 28 SWG.
Right now, I'm using the quickest solution of setting the pins to INPUT, it would be a long term problem? Stability and durability are important.
Right now, I'm using the quickest solution of setting the pins to INPUT, it would be a long term problem?
No that would be fine, I was just saying that it is simple to make changes to a PCB.
When I worked as an electronics designer, due to the complexity of the circuits, and the component's packages ( like 200+ connection BGAs ) it was impossible to prototype a board, so we got a PCB made of the first design. Then when things needed changing we made modifications to that board like I said and those changes were incorporated into the next "spin" of the PCB. The standard procedure involved having three spins to get to the final production prototype PCB.
I would still recommend connecting the contrast pot to your Vcc of the LCD instead of connecting it to 5V, to remove any leakage to the display when it is powered down. A simple cut and wire link should be fine and if you are not making many you can leave it at that.
Grumpy_Mike:
No that would be fine, I was just saying that it is simple to make changes to a PCB.
When I worked as an electronics designer, due to the complexity of the circuits, and the component's packages ( like 200+ connection BGAs ) it was impossible to prototype a board, so we got a PCB made of the first design. Then when things needed changing we made modifications to that board like I said and those changes were incorporated into the next "spin" of the PCB. The standard procedure involved having three spins to get to the final production prototype PCB.
I would still recommend connecting the contrast pot to your Vcc of the LCD instead of connecting it to 5V, to remove any leakage to the display when it is powered down. A simple cut and wire link should be fine and if you are not making many you can leave it at that.
The contrast pot can be easily changed, because of the components and traces disposition, I will really consider doing what you suggested.
To think that so much knowledge and experience would be earned from a simple post!
