I am trying to power up MKR1000 with a dc-dc boost converter (3V in, 5VDC out, spec up to 300mA), but it seems like the the converter does not keep constant current of about 110mA, so MKR1000 cannot run its WiFi module. Would anyone have a suggestion to allow using the dc-dc ?
thanks much
You shouldn't expect "constant current". Are you actually measuring current?
With 110mA out you'll need more than 180mA in (conservation of energy theory) and if your 3V source can't supply that, you won't have 3V anymore.
Is the 5V output holding-up? (I assume not.) Is the 3V holding-up? What is the 3V source?
The DC-DC converter could be bad or it could just be "cheap".
As DVDdoug suggested you may not have enough 3.3V power to accomplish what you need.
If you don't have test equipment handy you might try running the DC-DC from two fresh AA alkaline batteries. If it works with the AA batteries then you know the original 3v source is not capable of the power you require.
Thanks for the suggestions.
I used the two AAAs first, but when i started having problems, i switched to the lab power supply. It is set to limit at 400mA. I use raw 5V input to MKR1000. The 3V supply to DC-DC input is solid. The output 5V is solid above 3V inputs.
Even with the lab power supply, when i connect a DVM tot he DC-DC, i see current vary from 30mA to 150mA, staying mostly at 30mA. 5V seem to be OK if i feed the DC-DC with a voltage above 3V. One time the voltage dropped from 5V to 2.4 and stayed there, but this was with 1V input to DC-DC (the DC-DC is spec'd to work from 1V to 5V input)
So, now my setup is: 2.8V from the lab PS going to DC-DC. Output 5V seems solid, but current jumps around. If I use just use the lab PS w/o DC-DC, the current reads 110mA and the WiFi works.
I tend to agree that it could be just a cheap DC-DC board. Just thought maybe someone already ran an Arduino Wifi board with a DC-DC boost and can a good DC-DC. I guess, being lazy and cheap is not working out for me :).
Thanks, again.
Output 5V seems solid, but current jumps around.
Yes, that sounds correct.
Boost converters usually have 2 current specs.
One is the maximum output current and the other is the maximum input current which is determined by the switcher chip.
Its possible that the WIFI card draws more current when its transmitting than when idle, but the duration of the increased current is too short to read on an analog current meter, so the boost converter isnt able to supply the short term current so drops out of regulation and the 5V rail falls.
Do you have a CRO and can you look at the output voltage of the boost converter.
Hello,
Thank you all.
I characterized the part with a 50 ohm resistor as a load; have not looked at it with a scope yet. But i see it delivering 90 mA into 50 ohm at Vout=5V if Vin is above 3V. I was expecting 100 mA.
I tend to agree with MarkT that the WiFi duration might be too short for the Dc-DC to catch up. I'll check the scope readings and get a better DC-DC. this way i can use a DC-DC for $2 and two AAA for $0.50 instead of $10 Li-Po.
thanks
The MKR1000 is designed around a LiPo battery, and includes a MCP73830 charger chip.
It makes sense to go cheap with a $2 Nano clone, but I wouldn't fiddle with a MKR1000.
Leo..
90 mA into 50 ohm at Vout=5V
One (or more) of those values is wrong...