As the title say:
Is there limit powering Arduino, a bluetooth module(hc-05), a lcd on and off to save battery, like 4 sec off, 1 sec on for continous 24/7
Even is there is no limit is this method safe?
As for arduino i can sleep him but for the bluetooth module and the lcd module i can't sleep them only to power them down with a npn
You can power every module on/off, but better at the "hot" side - don't switch the Gnd line.
I'd choose the right modules, like a BT module with sleep functionality, and a LCD display without backlight. Many LCD displays (wrist watch...) can work many months from a coin cell, no need to turn them on and off.
Generally speaking it is the heating and cooling associated with switching devices off and on that shortens their lives. But I suspect that will not be the most pressing concern for your project.
...R
DrDiettrich:
You can power every module on/off, but better at the "hot" side - don't switch the Gnd line.I'd choose the right modules, like a BT module with sleep functionality, and a LCD display without backlight. Many LCD displays (wrist watch...) can work many months from a coin cell, no need to turn them on and off.
I found it hard to switch from high side as a beginer
Can you give me some reasons why i shoudn't use the npn method for this case?
Also i only switch the bluetooth module on/off for 24/7 not the lcd
Thanks for your reply
Robin2:
Generally speaking it is the heating and cooling associated with switching devices off and on that shortens their lives. But I suspect that will not be the most pressing concern for your project....R
There are no buttons i only need to scan bl.devices with the bluetooth module every 4 sec it also won't get hot or something. So from your point of view there is nothing wrong.
Thanks for all your replys
A npn transistor to ground adds its saturation voltage of about 0.4V, a FET would work much better. For a simple high side switch a pnp transistor can be used.
A BT module in sleep mode shouldn't consume much power, and will wake up on receipt of a message.
prologikus:
also won't get hot or something. So from your point of view there is nothing wrong.
Of course its internal temperature will change when it is switched on and switched off. I did not mean that it would get hot in the sense that you might be able to detect it with your finger.
...R
Can you give me some reasons why i shoudn't use the npn method for this case?
- because your ground would not be a true ground, as mentioned in #4
- because the chip could latch up.
- because you can get parasitic grounding
- because it is a good way to damage a chip.
- because it will not always work.
All of the HC-05 and HC-06 BT modules I have have an enable pin to power them down.
lg, couka
couka:
All of the HC-05 and HC-06 BT modules I have have an enable pin to power them down.lg, couka
What is the name of that pin ?
It's labeled "EN" if I remember correctly.
lg, couka
couka:
It's labeled "EN" if I remember correctly.lg, couka
Nope, the EN is actualy the KEY pin
When it set to high and the device is powered on it enter the AT mode(the mode that i use to search for my phone)
if is low then it enter communication mode where you can send commands between bl devices
I've used that Pin to save energy in a remote control application. On my modules that pin is connected to a 3V3 voltage regulator on the breakout-board, which powers down.
Maybe there are boards with different pinouts.
lg, couka
couka:
I've used that Pin to save energy in a remote control application. On my modules that pin is connected to a 3V3 voltage regulator on the breakout-board, which powers down.
Maybe there are boards with different pinouts.lg, couka
first, there is no power saver mode for my module
from the datasheet of the hc03, hc05(left), hc06(right)
second, i also have a 3.3v regulator but none of those 6 pins(V+,Ground,TX,RX,EN,State) can power it down
maybe i can connect to that regulator and stop it but is a tiny tiny one and i don't know how i can do it, as you did
The datasheet of the bare hc0X modules doesn't really matter, since the power-down-mode is a function of the breakout-board.
Anyways, DrDiettrich already suggested using a PNP to cut power to the module, which has the same effect and works with all of them.
lg, couka
couka:
The datasheet of the bare hc0X modules doesn't really matter, since the power-down-mode is a function of the breakout-board.Anyways, DrDiettrich already suggested using a PNP to cut power to the module, which has the same effect and works with all of them.
lg, couka
DrDiettrich:
A npn transistor to ground adds its saturation voltage of about 0.4V, a FET would work much better. For a simple high side switch a pnp transistor can be used.A BT module in sleep mode shouldn't consume much power, and will wake up on receipt of a message.
Successful builded a pnp switch like in a schematic, a double one, but the overall current increased by 1 or 2 mA, but is not a problem as long as this circuit won't damage my bl as the npn method
You can omit the NPN, simply connect the digital output to the 1.8k resistor. And invert the logic, now a LOW output will enable power to the module.
DrDiettrich:
You can omit the NPN, simply connect the digital output to the 1.8k resistor. And invert the logic, now a LOW output will enable power to the module.
lol
After i struggled to make it 
.. :s
I thought the PNP needs to be connected to a ground in order to work
A NPN is needed only as a level shifter, if the module supply voltage is higher than the Arduino HIGH output voltage. Or if it has to provide more base current to the power PNP than the digital output can supply.
DrDiettrich:
A NPN is needed only as a level shifter, if the module supply voltage is higher than the Arduino HIGH output voltage. Or if it has to provide more base current to the power PNP than the digital output can supply.
Thanks for all your help, the case is now solved
PS; it wasn't easy to unsolder the npn's and resistors from the module but i think the work made me learn the lesson