Can the Boost board be stacked?

[sgllama]

I've finally getting some spare time to make up a few Digispark kits - having got to the bost kit, I was hoping to use this with a LED board (RGB or Charlieplexed), so the LED obviously should be on top - which means that the boost has to be bottom-most or stacked in the middle.

But neither the female headers nor the stackable headers (in the kits or that I've so far found advertised in the UK) are tall enough to raise clear of the inductor.

However, if the boost were a wee bit longer, the header positions could be moved along so that P5 is in the position now occupied by P3. That gives enough clearance for a Digispark fitted with stackable headers to plug into the boost. Holding the parts in a rough dry fit, there wouldn't be any fouling of the USB port.

Meanwhile, with the boards we've got, has anyone used the boost board with an LED project and come up with a clever solution?

Stephen

[scruss]

I wouldn't describe this as a clever solution, but it does work:

Headers on boost shield are cut-down Arduino stackable headers. Next time, I wouldn't have them quite so tall (or so squint).

[Bluebie]

My solution ended up being not to use the boost shield and instead use 9v batteries connected straight to VIN and Ground. It's less energy efficient, but you don't need as many little thingies and a digispark powering 6 addressable RGB Flora NeoPixel LED thingies running at 16mhz will run for about 4 hours on a rechargable 500mah 9v battery or about 8 hours on a high end disposable one.

[Mark]

jenna
Did you try swapping the normal regulator for the low drop out version.?
Its great that Erik has used these as they at least allow a 30V input range rather than the 14-15v for normal Arduino.

This in theory should give you a bit more as it only needs 160mV (5.160v) to keep giving 5v out.


Mark

[Bluebie]

The Digispark keeps running fine right down until it's supply voltage reaches 2.8v where the brownout protection activates. My LEDs start becoming dimmer around 3.5v. The lithium ion chemistry of my 9v batteries mean the voltage remains fairly stable and suddenly drops right near the end. Therefore the difference of half a volt or so drop through the regulator has nearly no impact on runtime.

[Mark]

Okay ..
What surprises me is that the regulator continues to provide volts.
The standard ones have a 2v dropout, meaning that they usually stop providing 5v out, when the input drops below 7v.

The LDO versions stop at 5.160v.

As you say the discharge curve is also flat, so its not going to change the end result.


Mark

[Bluebie]

Experimentally the regulator on the digispark outputs 5v or (VIN - roughly 1.42v), whichever is lower. The regulator seemed happy to provide power with that fairly constant voltage drop under load of about 200ma peak to PWMing LEDs cycling through rainbows.