Flickering (timer problem?) when connected to an USB power adapter

I programmed a small smooth LED glow (pulse-based dim with modulation of the ratio) as a small test. It is running really smooth as long as the Espruino board is connected to my MacBook.

However, once I plug it directly into an usb power adapter (tried several) I get bad flickering of the LEDs during the otherwise smooth anmation.

I wonder if this is a broken board or just a capacity problem, and whether adding a quartz will help in this particular case.

Any ideas before I go and buy one?

Cheers
Stev

This could actually be an issue with your adaptor... It's been reported a bit before - Espruino draws so little power that the adaptor thinks it isn't connected to anything, and it keeps turning itself off.

If you have a high-ish wattage 10 ohm resistor, you could put that across the gnd + bat connectors on Espruino. That'll draw ~0.5 amps which should easily force the charger on. Failing that you could try plugging a USB hub in, and charging a phone on the charger at the same time :)

Funny. Didn't think of that. Will see how that works out. And if that's actually the culprit :)

Seems my passive hubs here don't provide enough power for my iphone to register. I will see what turns up quicker, a powered hub or that resistor and post the result.

To not build a useless heater, i'll have to get a battery and use that trickle charger setup, it seems. Nice HW design BTW, always nice to see things already in place once you think you might need them.

By the way, you probably don't need such a massive resistor - just something that'll draw more than the ~20mA that Espruino will be drawing.

Thought that too. .5 amps seemed a bit "safe" :)

I had a similar issue when using a solar charged battery. The battery kept turning itself off after ten minutes due to such small current draw .

Too efficient!

:) After having looked inside, some of the cheap solar chargers are quite scary (especially where the 'charging' circuit is).

I've got one here where I have just removed the circuit board and connected the solar panel across the battery. It works great!

Only problem then is stopping overcharging, but with smaller solar panels it's probably not something you'll have to worry about.

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Well, unfortunately I had less success, neither with the hub approach nor the resistor idea. I'll see what the oscilloscope view on bat-gnd will bring over the weekend.

I have noticed flickering in PWM-controlled LEDs (external LEDs driven off a ULN2803, also on an external breakout board) when running off a benchtop power supply with stable output voltage and controlled by bluetooth It happened only after some time had passed, and I could see the current change as it did (these were 1W leds >.>). I'd set them with analogWrite(pin,1); so they should have been on full time anyway....

So there may be a deeper issue here. I won't say my results are meaningful until I've re-run it with proper heatsinking on the LEDs and driver (they both get pretty hot) - I have a heatsunk setup assembled, but have not driven it from Espruino yet.

I have ruled out loose connections, though, as the flickering does not react to jiggling the wires.