This works great when attached to a pc via USB, showing data packets via serial.
However, if I run the Mega from a USB charger, it stops receiving.
If I power the board from a 9v wall wart on the power socket, it starts working again...
I initially wondered if Serial was hanging with nothing on the USB other than power, but it appears that, for some reason, the 433 module stops receiving or receives garbled data when connected to a USB charger power source.
I tried two different chargers.
It's not really a problem as the external power socket works fine, but I was curious why using USB power would cause this and only when not connected to a PC.
richardtheboffin:
I tried 2 different USB chargers. (2A). I guess it must be an emc issue...
There's an SD card reader and a realtime clock in addition to the 433 receiver.
Are these 'chargers' as you are calling them actually USB power banks ?
It helps to be clear on what you are using.
I have a 5v USB power supply which I can connect to my mobile phone and it will charge from the power supply. But the 5V USB power supply is not a charger, its just a power supply, the charger part is in the phone itself.
srnet:
Are these 'chargers' as you are calling them actually USB power banks ?
It helps to be clear on what you are using.
I have a 5v USB power supply which I can connect to my mobile phone and it will charge from the power supply. But the 5V USB power supply is not a charger, its just a power supply, the charger part is in the phone itself.
Not sure how to be more specific. They are chargers for phones/kindles/tablets etc. They output 5v DC. Plug into the mains.
They work fine for running the Mega2560 except that for some reason the 433mhz reciever doesn't see any valid data. I will double check that actual voltage on the 5V rail though...
Plug in a cheap'n'nasty 9v wall wart and it starts getting data. Plug in a PC so that the board is powered via USB and again, it works fine.
richardtheboffin:
Not sure how to be more specific. They are chargers for phones/kindles/tablets etc. They output 5v DC. Plug into the mains.
So there not chargers, but 5V power supplies, there is a differance.
A lot of USB power banks are switching devices to convert the low voltage of a Lithium battery up to 5V for powering a 5V USB device. Some of these can cause enough EMC to have a significant effect on UHF radio reception.
srnet:
So there not chargers, but 5V power supplies, there is a differance.
A lot of USB power banks are switching devices to convert the low voltage of a Lithium battery up to 5V for powering a 5V USB device. Some of these can cause enough EMC to have a significant effect on UHF radio reception.
Errrrm, there are no batteries in these chargers, you plug them into the mains. They charge your phone/tablet/other device via the USB socket. You must have seen one????
I don't really want to get into the symantics of when a charger is a charger and when it's a power supply... In my book a charger is something that charges a battery powered device. You can argue that the power brick for a laptop is a charger or a PSU. It's both. If the PC is off, it charges the battery...
Anyway if you go into a shop and ask for a phone power supply, I'm not sure anyone would understand what you were talking about. Ask for a phone charger and you'll get a 5v output USB charger...