Hi there,
I bricked two A-STAR 328PB while using VCCIN as a power source.
Are there any special considerations regarding the power connections?
To power the system, I connected VCCIN and GND pins. VCC, VBAT, VCC are not connected.
The linear power source is regulated and rock stable at 5V. The A-STAR’s worked correctly as long as I do not connect anything externally.
I prototyped the schematics on a breadbord and it worked flawlessly (with an Arduino Nano).
Cannot spot/measure any short circuits.
Kind regards,
Christoph
CAPAmp01.pdf (93.0 KB)
Hello, Christoph.
How do you know that your A-Star 328PBs are bricked? What were you doing before the issue happened? What are you connecting to the A-Star that causes it to not function properly? Do the A-Stars work again if you disconnect everything? What AVR programmer are you using? Can you post your schematic and picture showing how everything is actually connected in your setup?
- Amanda
Hello Amanda,
thanks for your quick response.
I know that I bricked them because they started taking about 1.5 A, became really hot and do not respond to anything anymore… 
I assume a mistake on my side but cannot find any problem with my schematic. Hence my question whether I would need to take any special measures when connecting the A-STAR to VCCIN.
After checking the schematic and the actual board, I started as follows:
(1) Hookup A-STAR board without any peripherals or other ICs populated, connect VCCIN --> The Board worked properly, blink test ok
(2) Add 74HC14Schmitt Trigger, connect VCCIN --> A-STAR did boot up, LED blinked, after some seconds, the system became hot and drew 1.5 A @ 5 V --> Dead. Does not work with everything disconnected.
I then re-checked everything multiple times and it seemed to be ok
Second try with another (new) A-STAR board:
(1) Hookup A-STAR board without any peripherals or other ICs populated, connect VCCIN --> The Board worked properly, blink test ok
(2) This time connect no 74HC14 but a MCP23S08 board via SPI, connect VCCIN --> A-STAR did boot up, LED blinked, after some seconds, the system became hot and drew 1.5 A @ 5 V --> Dead. Does not work with everything disconnected.
The SPI board is perfectly ok and in use in other projects without problems.
Before starting the above tests I checked for short circuits without/with populated sockets on the board, no obvious issues.
I attached my schematic which resembles the components I have on the board. For the tests I used a linear power supply, VCCIN = +5V in the schematic.
So basically I wonder if I just can connect VCCIN to 5V of power or if I need to take any precautions before doing this.
Tools:
- Pololu A-STAR 328 PB Micro 5V/16MHz
- Pololu AVR Programmer v2.1 (disconnected during my tests)
- Linear lab power supply (5V) with voltage/current display
Thanks again,
Christoph
It does sound like there is something in your system that is causing the problem. When you tested the A-Star 328PB with the 74HC14 Schmitt Trigger, were you connecting them through your board?
It is not clear from your schematic how your A-Star is connected. The schematic seems to show some supporting components connected to an ATmega328PB, but they do not match the ones on the A-Star:
Do you have a schematic that is more representative of the actual connections you have made? Can you share a photo of the A-Star as you have it connected in your system?
Yes, you can supply 5V to the VCCIN pin on any of the 5V versions of the A-Star 328PB board. The VCCIN pin bypasses the regulator, so it is important for the voltage on that pin to match the regulator voltage for the A-Star 328PB version you are using. You can find more details under the “Power” section of the A-Star 328PB User’s Guide.
- Amanda
