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Partly offtopic - LCD --> Relay --> Power

Started by gm March 21, 2016
Hi to all.

I've started to create schematics for PCB board that will be plugged 
onto arduino mega board. All pins are set on bottom double connector to 
simplify pcb design and all power( for arduino board / LCD, coin machine 
/ relay/ keypad etc.) will come from this board. Main external power 
source will be 12V transformer ( cca 40W, standard ).
--------------------------
When i was testing the whole project i run on one possible problem.
If i power arduino board ( for now, still over USB ) system starts OK 
and welcome message is displayed correctly, but when i plug power for 
relay ( which is powered from external 12VDC power adapter *for 
now*),LCD start to output random characters and signs. This will not 
happen if i start relay power source, first.

I dont know if this will happen when the PCB is done and when you will 
have one mayor power source,but it could be a problem..

In end effect, i can start reley first and then arduino, but i dont know 
why is this happening. Relay is connected over BC547 and diode so there 
shouldn't be any problem.

---------------------------------------------------------------

2.)I'm using sainSmart arduino mega board.
What is the optimal external power source for this board ?
Can i power it with 9V or maybe 12V ?. On they web site is mentioned 
that there is a voltage range from 7-12V so 9V should be optimal 
solution ?. Any practical suggestions ?
On 21/03/2016 4:06 PM, gm wrote:
> Hi to all. > > I've started to create schematics for PCB board that will be plugged > onto arduino mega board. All pins are set on bottom double connector to > simplify pcb design and all power( for arduino board / LCD, coin machine > / relay/ keypad etc.) will come from this board. Main external power > source will be 12V transformer ( cca 40W, standard ). > -------------------------- > When i was testing the whole project i run on one possible problem. > If i power arduino board ( for now, still over USB ) system starts OK > and welcome message is displayed correctly, but when i plug power for > relay ( which is powered from external 12VDC power adapter *for > now*),LCD start to output random characters and signs. This will not > happen if i start relay power source, first. > > I dont know if this will happen when the PCB is done and when you will > have one mayor power source,but it could be a problem.. > > In end effect, i can start reley first and then arduino, but i dont know > why is this happening. Relay is connected over BC547 and diode so there > shouldn't be any problem. > > --------------------------------------------------------------- > > 2.)I'm using sainSmart arduino mega board. > What is the optimal external power source for this board ? > Can i power it with 9V or maybe 12V ?. On they web site is mentioned > that there is a voltage range from 7-12V so 9V should be optimal > solution ?. Any practical suggestions ?
Most Arduino boards I have seen can be directly powered by a 5v source. The 9v etc is when the board is powered through the DC power socket which feeds a 5v regulator. Have you commoned the grounds of the Arduino and the 12v supply ?
On Monday, March 21, 2016 at 4:06:14 AM UTC-4, gm wrote:
> Hi to all. > > I've started to create schematics for PCB board that will be plugged > onto arduino mega board. All pins are set on bottom double connector to > simplify pcb design and all power( for arduino board / LCD, coin machine > / relay/ keypad etc.) will come from this board. Main external power > source will be 12V transformer ( cca 40W, standard ). > -------------------------- > When i was testing the whole project i run on one possible problem. > If i power arduino board ( for now, still over USB ) system starts OK > and welcome message is displayed correctly, but when i plug power for > relay ( which is powered from external 12VDC power adapter *for > now*),LCD start to output random characters and signs. This will not > happen if i start relay power source, first. > > I dont know if this will happen when the PCB is done and when you will > have one mayor power source,but it could be a problem.. > > In end effect, i can start reley first and then arduino, but i dont know > why is this happening. Relay is connected over BC547 and diode so there > shouldn't be any problem. > > --------------------------------------------------------------- > > 2.)I'm using sainSmart arduino mega board. > What is the optimal external power source for this board ? > Can i power it with 9V or maybe 12V ?. On they web site is mentioned > that there is a voltage range from 7-12V so 9V should be optimal > solution ?. Any practical suggestions ?
That's hard to follow. A simple picture of the output part would help. AFAIK arduino's output only 5V and need only that to run, powering it from more voltage, means a voltage regulator somewhere. If you need more voltage to turn something on, then a separate power supply for that perhaps. Depending on the load that could be a single transistor. George H.
Hi guys, sorry for late reply.
This is the board that am using ( please look at characteristics )

http://www.sainsmart.com/sainsmart-mega2560-r3-development-board-compatible-with-arduino-mega2560-r3.html

The module should be fully independent and it will be powered from 
external AC source (transformer ). The board that will be placed onto 
this arduino will have:
  - 5V
  - 9V
  - 12V
DC outputs,because of different external parts that need this kind of 
voltage. But what i dont get is the operating voltage range of arduino 
board. From 7 - 20V.

So according to this, 9V would be some optimum solution.
If you can please check this part fist, then i can explain in more details..




On 22.03.2016 02:10, George Herold wrote:
> On Monday, March 21, 2016 at 4:06:14 AM UTC-4, gm wrote: >> Hi to all. >> >> I've started to create schematics for PCB board that will be plugged >> onto arduino mega board. All pins are set on bottom double connector to >> simplify pcb design and all power( for arduino board / LCD, coin machine >> / relay/ keypad etc.) will come from this board. Main external power >> source will be 12V transformer ( cca 40W, standard ). >> -------------------------- >> When i was testing the whole project i run on one possible problem. >> If i power arduino board ( for now, still over USB ) system starts OK >> and welcome message is displayed correctly, but when i plug power for >> relay ( which is powered from external 12VDC power adapter *for >> now*),LCD start to output random characters and signs. This will not >> happen if i start relay power source, first. >> >> I dont know if this will happen when the PCB is done and when you will >> have one mayor power source,but it could be a problem.. >> >> In end effect, i can start reley first and then arduino, but i dont know >> why is this happening. Relay is connected over BC547 and diode so there >> shouldn't be any problem. >> >> --------------------------------------------------------------- >> >> 2.)I'm using sainSmart arduino mega board. >> What is the optimal external power source for this board ? >> Can i power it with 9V or maybe 12V ?. On they web site is mentioned >> that there is a voltage range from 7-12V so 9V should be optimal >> solution ?. Any practical suggestions ? > > That's hard to follow. > A simple picture of the output part would help. > AFAIK arduino's output only 5V and need only that to > run, powering it from more voltage, means a voltage regulator > somewhere. > > If you need more voltage to turn something on, then a > separate power supply for that perhaps. > Depending on the load that could be a single transistor. > > George H. >
On 21/03/2016 08:06, gm wrote:
> Hi to all. > > I've started to create schematics for PCB board that will be plugged > onto arduino mega board. All pins are set on bottom double connector to > simplify pcb design and all power( for arduino board / LCD, coin machine > / relay/ keypad etc.) will come from this board. Main external power > source will be 12V transformer ( cca 40W, standard ). > -------------------------- > When i was testing the whole project i run on one possible problem. > If i power arduino board ( for now, still over USB ) system starts OK > and welcome message is displayed correctly, but when i plug power for > relay ( which is powered from external 12VDC power adapter *for > now*),LCD start to output random characters and signs. This will not > happen if i start relay power source, first. > > I dont know if this will happen when the PCB is done and when you will > have one mayor power source,but it could be a problem.. > > In end effect, i can start reley first and then arduino, but i dont know > why is this happening. Relay is connected over BC547 and diode so there > shouldn't be any problem. > > --------------------------------------------------------------- > > 2.)I'm using sainSmart arduino mega board. > What is the optimal external power source for this board ? > Can i power it with 9V or maybe 12V ?. On they web site is mentioned > that there is a voltage range from 7-12V so 9V should be optimal > solution ?. Any practical suggestions ?
My guess is that the relay powering up is causing the processor to crash, probably by spiking the supply. How is the relay driven? Is there a flyback diode across the coil? If that doesn't mean anything to you, Google 'relay flyback diode'. Cheers -- Syd
On 03/22/2016 05:01 AM, gm wrote:
> Hi guys, sorry for late reply. > This is the board that am using ( please look at characteristics ) > > http://www.sainsmart.com/sainsmart-mega2560-r3-development-board-compatible-with-arduino-mega2560-r3.html > > > The module should be fully independent and it will be powered from > external AC source (transformer ). The board that will be placed onto > this arduino will have: > - 5V > - 9V > - 12V > DC outputs,because of different external parts that need this kind of > voltage. But what i dont get is the operating voltage range of arduino > board. From 7 - 20V. > > So according to this, 9V would be some optimum solution. > If you can please check this part fist, then i can explain in more > details.. >
The Arduino has an onboard linear 5 volt regulator on the power jack. You need to allow for the drop across the regulator so 7V is the minimum, anything above that just increases the dissipation of the regulator. Use of 9V is common because 7V supplies are not so common.