Discussion in "Hardware" started by    zhudao    Dec 5, 2017.
Tue Dec 05 2017, 06:41 AM
#1
Hi to all, in the period time I'm doing an project, some questions I need to help. I am working in a project for getting data from a Load Cell, in the project I use a very good Shield built by a very good friend, this shield has a PGA (Programable Gain Amplifier), a Fast ADC chip, and a voltage regulator (to get 5.0 +/- 0.1 V). This shield is over an Arduino Uno, and when I get a command from Serial port I start getting and printing the time and the load cell voltage data each 1 ms, and this is working pretty nice!.

The Arduino is powered by a 120 AC to 5VDC adapter (see the photo attached), this 5 VDC are elevated to ~8 VDC by a

LM2587S-DC-DC-Step-Up-Adjustable-Boost-Power-Supply-Module-Converter-Regulator, see this link

https://www.ebay.com.au/itm/LM2587S-DC-DC-Step-Up-Adjustable-Boost-Power-Supply-Module-Converter-Regulator-/192262886299

this was because of I wasn't able to get a 120 AC to 8 VDC adapter, and these 8 VDC (I need 8 volts for the 5.0 V regulator mentioned above) are plugged into the jack power conector of the Arduino Uno,

The data from the serial port goes to a USB to Serial Rs232 cable converter, this use a PL2303HX chip (look the link down), and this is conected to the pc with a 3 m USB extension

https://www.amazon.com/Armorview-PL2303HX-Cable-Module-Converter/dp/B008AGDTA4

The problem is that this is the second time that I heard something like an electric short and all the things conected to the Serial port is damaged, I mean the PC USB port, the Serial to USB cable Converter, the Arduino (once) and the Arduino serial port (in the other time).

Looking for what happened I opened the USB to Serial Cable and I saw something like a fingerprint of a spark (see the photos attached), and how you can see this happened in the power line. According to this I guess that this was an overvoltage or an overcurrent in the PC usb port, but the other things like mouse and keyboard didn't fail.

I was wondering if someone could help me to understand what happened, I appreciate any idea.

This is a block diagram of my circuit

I don't need exactly 8 volts, but I need 7 V or more for the power jack to power the Arduino, so I choose 8 volts, I use the booster because I couldn't find more than 5V or 12V adapters, and with the 12V regulator of the arduino gets pretty hot, so I prefer to use the booster.

The damage was in the power lines, and for that reason I guess that was an over voltage or over current from the pc USB port
I had purchase a better supplier USB-TTL cable from SEED, but I buy it from Digikey,
I know this is not as good as Adafruit once, but I am in Japan and it is really difficult to get this things because I have to pay for shipment and some taxes when it get into the country

excuse me for all the comments in the same answer.
Thank you!
Tue Dec 05 2017, 08:12 PM
#2
I think either your 120 - 5 volt adapter, or the LM2587S is at fault.
Have you rechecked the output voltage of both of them ?

You my have mains leakage current from the mains adapter.
Get something else, it could be dangerous.
The old type with heavy transformers are safer, ideally double insulated.

You do not show smoothing capacitors on the power supply.
The LM2587S may become unstable without proper capacitors on the
input and output.




Wed Dec 06 2017, 03:08 AM
#3


I think either your 120 - 5 volt adapter, or the LM2587S is at fault.
Have you rechecked the output voltage of both of them ?

You my have mains leakage current from the mains adapter.
Get something else, it could be dangerous.
The old type with heavy transformers are safer, ideally double insulated.

You do not show smoothing capacitors on the power supply.
The LM2587S may become unstable without proper capacitors on the
input and output.





ExperimenterUK


actually, I'm not recheck voltage, thank u!

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Mon Nov 05 2018, 09:48 PM
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