As the title says, i am in a middle of a project with DCF77 module on UNO board but having problems with power supply.
So, on random some wall wart power adapters are less noisy and i can pick up a clean signal, some are more noisy and i am getting messy signal....
So i have a wall wart 9V, then DC/DC Buck converter that feeds directly to UNO 5V pin.
One strange thing i cant explain and would like to know more if someone can help... ehn i connect USB cable to UNO it starts receiving clean DCF77 signal, as soon as i take it out it goes messy again.
So the question is, what does that USB connection does to UNO to basically eliminate the noise that interferes with my DCF77 receiver?
So i have buck converter feeding UNO all the time, but DCF77 signal is clean and stable only if USB is connected as well.
Is there a way to "simulate" that USB connection with something else to reduce noise?
I have tried dozens of buck converters, with LC filters, capacitors... everything i could find, results are the same: if i have quality power supply like laptop charger, it all works but as soon as i use regular wall wart it all goes down hill.
I would like to be able to use just any power supply if possible without having to worry about noise.
aarg:
What happens when you feed the 9V into Vin instead of using the buck regulator, so that the UNO onboard linear regulator is used?
Same thing happens. The problem is, i have another board, MEGA, with 7seg displays (max7219) on it, and boards have common ground as i need to feed DCF77 signal to MEGA board.
As i said, some power supplies work and some dont, i guess those that do have some sort of internal filter or something... whatever i try i can't reduce the noise for all power supplies (wall wart adapters)..
DrDiettrich:
Have you checked the 5V with a scope? Some wall warts are known to interfere with DCF77 even from different floors.
If you say that DCF77 signal is received when powered from USB then it may be due to a bigger antenna ground plane supplied by the USB connection.
Unfortunately i do not have a scope, i think now is the time to get one.
The problem goes beyond USB. I have 3 wall warts, random selection, one is a charger from 15 years old DELL laptop, when i use this one via buck converter, i have NO interference at all! Signal is picked up right aways, clean and stable no USB connected to UNO of course.
Next one is from an old external HDD, 12v 1500mA, disaster, i get error for every single bit of DCF signal.
Next one is random pick from Amazon, 9V, 2A.... works almost as good as laptop charger.
last one is "regulated" 9V 3.5A, not a cheap one either, this one is not a disaster but makes 3-10 errors in DCF bits every minute.
All adapters tested on the same power outlet and the same buck converter. Also as i mentioned, i have 5-6 different buck converters, they all have LC filters, different specs but all very consistent... everything seems to point and depend od INPUT power source.
aarg:
Does the MEGA share the same power supply as the UNO? There is no doubt the MAX7219 might be interfering.
Yes they do, and yes i am aware MAX7219 are very noisy BUT, i have to use one power supply as i need the signal from UNO processed in MEGA, or at least i need common ground, but even with the common ground i still have the same results. I have tried to have separate buck converter for UNO, fed from the same wall wart as MEGA, but as long as i have common ground, same thing happens.
Again strage thing, with all the MAX displays and everything, as soon as i plug in the USB into UNO, signal is amazing and everything is perfect. Even with both 5V and GND connected to MEGA, as soon as i plug in USB, everything works...
For those without an oscilloscope, you can detect most electrical noise with an audio amplifier and speaker. Connect audio input to the noise source THROUGH A CAPACITOR. Turn up the amp. Turn on the noise source. A good power supply will make a single click when you turn it on. A bad PSU will create noise in the audio amplifier output.
my dcf antenna was cca 1m from my rig, i have move it another metwr away and now ALL power supplies work! very naive of me to think it would work so close, but still with some PSUs it did. Also, i have 15 MAX7219 chips on my rig so i guess that as well is very considerable noise.
now one more issue, i have a digital encoder to control display brightness and a light diode for automatic brightness, so when i swith from automatic to encoder, and when i turn encoder i loose signal lock but it gets back the next minute. then it hold the signal for as long as i dont touch encoder. sometimes i can adjuat brightness with encoder without loosing signal lock but moat of the times it gives me a bit error. i was not aware encoder also produces noise?
One more thing, i am currently supplying 3V to my DCF77 antenna, while it can ge fed by 3-12V, would it improve reception/signal strength if i use higher voltage to antenna module?
If noise problems can not be resolved with the standard "textbook" methods, the entire system has to be examined closely. The best way to do that in a forum, is to post clear close up images of all the wiring, along with a complete schematic.
aarg:
If noise problems can not be resolved with the standard "textbook" methods, the entire system has to be examined closely. The best way to do that in a forum, is to post clear close up images of all the wiring, along with a complete schematic.
Yes, but unfortunately i do not have a full schematic of my setup, however i there are a couple of things here:
I think i did everything by the book with decoupling each MAX7219, LC filter on power supply...
I know that MAX7219 makes noise and i have 15 MAX chips in mys setup, so i guess considerable noise
Moving the DCF77 antenna module further away from my rig solved the issue as it should as by all standards and recommendations DCF antenna should never be anywhere near LED displays and Arduino boards in general...
BUT, i have noticed one more thing... i have 8 genuine MAX7219 chips on custom PCBs which turn on first even before i get the signal and 7 cheap matrix displays with knock-off MAX7219 chips, these turn on AFTER i get a lock on a signal . Not all of those 7 turn on at the same time but 3 of them, so i have a total of 11 ON at all times.
What happens is, when i restart everything, it powers up GENUINE MAX chips first, i have a fairly clean signal and get a lock after a minute or two and then as soon as non-genuine cheap MAX 7219 displays turn on, i start getting error bits and everything goes south.
Could this be possible that 8 genuine chips work fine with the signal and cheap ones immediately cause it to go crazy? IS the difference in noise so big that cheap chips could actually be the problem?
Not easy to test it out right away as i have 4 in 1 matrix modules on a single PCB with tiny, no name MAX chips.