temp probe issue when powering through LM7808

[JoBarTeam]

Hello,

Here are some data on my case:

Bluetooth
IR
LCD1602 + I2C
DS18B20 probe
Firmware 2.73
Aisler PCB drv8825 full options

Everything works fine against I have a small problem with the temperature sensor.

If I connect my focuser by USB + 12V the temperature sensor works very well like the rest.

If I connect my focuser by 12V + Bluetooth (LM7808 for Arduino) everything works also except the temperature probe which does not return value ( -- on the 1602 screen)

I tried with 2 different focusers, version 2.71 and 2.73 and the problem is the same.

Do you know where the problem might come from?

thanks a lot

[brownrb]

Seems my message did not go through,

You purchased this board correct?
https://aisler.net/p/UGHLNFJC

Please send me the frmware file you used to program the controller
Also, I need you to do following
1. Use 12Vdc and bluetooth (no usb cable)
2. Use Windows app
3. Enable logging
4. Connect to the controller
5. Wait till its finished connecting
6. Click get temperature - at the same time verify if the lcd is displaying -- for temperature
7. Close the windows app
8. Send me the logfile -

You can find me email address on line 22 of the firmware v273

[JoBarTeam]

Hi,

Yes this is the full IR+BT PCB rev 2 i'm using.

For the firmware I use the last 2.73 you upload.

I follow your steps and no display of temperature in the app and LCD.

Here the log

[EDIT] don't know if it's important but i don't use 10A10, 12V led and 12V switch.
I see that some users have this sort of issue when arduino is powered by external supply. Connecting sensor to arduino 3V3 may help.....

[EDIT2] I test with a 2K2 pull up resistor but issue is the same

[EDIT3] I measure temp prob voltage(+5V <--> GND) when using LM7808 and it's near 5V so i don't understand where the problem comes

[EDIT4] this is a photo of my board, do you think i have to move 12v pinout to another place ?

[EDIT5] i found a new thing, i´m using a 12v stepper motor with 12v external power supply. I can change the voltage on the power supply (see photo) and when i use the 6v position, the LCD don´t light a lot but i can see that the temp prob is working ! i dont understand nothing !

[JoBarTeam]

I take some measures:

out of the 12V power supply --> 12,13V
Where I connect my +12V + GND (like the photo) --> 12,04V
drv8825 VMOT --> 12,05V
LM7808 in 12,04V
LM7808 out 7,96V
Arduino +5V --> 4,90V
Temp prob +5V --> 4,90V
Temp prob SIGN --> 4,81V with 2,2K resistor
Temp prob SIGN --> 4,73V with 4,7K resistor

WIth USB i've
Temp prob +5V --> 4,53V to 4,59V
Temp prob SIGN --> move from 4,26V to 4,56V with 4,7K resistor

I try with different resistors but always OK with USB and not with 7808.

Damned, i'll not able to use temp prob and bluetooth.....

[brownrb]

I can see in the logfile
26/07/2018 13:12:53: CommandString: Sending Command :21#
26/07/2018 13:12:53: CommandString: Command :21#was sent.
26/07/2018 13:12:53: ReceiveString(): =START=========================================================
26/07/2018 13:12:53: ReceiveString: Command retcmd = Q
26/07/2018 13:12:53: ReceiveString: Buffer recbuf = Q0#
26/07/2018 13:12:53: ReceiveString: Value retstr = 0
26/07/2018 13:12:53: ReceiveString raw response for get tempresolution: Q0#

Should have been a value returned of 9, 10, 11 or 12 not 0 -

The way you have wired it, the way the 7808 works, the 7808 needs 12V in to be working, you cannot power on 6V using external supply. The 7808 will not turn on at 6V it needs at least about 10.4 to turn on and start working, so you have to power this using 12V.

I would be looking at a better PSU than 12V rated at 1.5A - you should be looking at 12V 3A instead

The pullup for the temperature must be 4.7V - there is no point measuring the SIG line.

Did you install all the libraries that cam with the firmware? You cannot use any other libraries or replace the libraries with other ones

I do not know what you mean by connecting sensor to 3.3V - there is no issues with the sensors running off 5V

Please send me your firmware file.

I also want you to try the following
In the firmware file turn everything off except TEMPERATUREPROBE and LCDDISPLAY then reprogram the controller.
Test with 12V - is temperature displayed on LCD
Test with USB only - is temperature displayed on LCD

[JoBarTeam]

Thanks !

When i powered with the 6V position with 7808 the LCD is not brighting but i see caracters and the prob work.
I've test with a 12V 15A and same issue, all the libraries are installed or replace with yours.

I've test to turn everything off but the problem remain.

Is it possible that i've a ground problem when using 7808 ? I've read that all arduino ground / external power ground / sensors ground have to go together. I dont use all components so i'm thinking of a discontinuated ground.....

Here is my firmare file

[brownrb]

For the 7808 to work, and supply voltage to the nano and sensors, it has to be powered by > 9.5V else there will be no output and the nano will not turn on.

If its working with a 6V supply then I can only assume there is something wrong with your board or you also have the usb cable connected. A 6V supply will not forward bias the 7808 regulator and the nano will not turn on. So if you have no usb cable connected and it appears to be working on 6V I suspect that there is something wrong with the wiring

[brownrb]

If you are using the PCB then all grounds are connected so there should not be any ground issue.

I would recommend that you recheck all your soldering and check for any shorts between wires caused by soldering. Use a large magnifying glass and a bright light torch shining on the board.

[Andreas Exeler]

Hi,
some 7808 have "Noise" on the output, please check the capacitor around the 7808.
With Noice on the 8V you get some strange values...
Greets
Andreas