Is it possible to power Dash Pro (assuming I’m not using USB or the battery charger) directly by connecting the 3.3V pin R12 to a regulated 3.3V source? Any problems with doing this?
Hi – any thoughts about this?
Thank you for the question. I apologize for the delay. My notifications got turned off during the AT&T Hackathon and CES, so I only just got this question. If you have any follow up questions, I’ll be much more responsive.
The Dash / Pro were designed to be powered by +5V / Battery, and don’t have a readily available way to be powered by +3.3V without modification. We are changing this on our next sustainability revision (As well as getting rid of the jumpers).
I’ve added pictures to show how to do the modification yourself. This is a one-way operation, you would lose the ability to use +5V in, or battery charging. This will be fixed on future revisions.
If you don’t feel 100% comfortable removing an 0402 resistor, please contact email@example.com and we can arrange to have a modified Dash or Dash Pro sent to you. You can also use a pair of diagonal cutters to cut the resistor in half, but that can get messy. This is absolutely something we can support in high volumes, if you need a solution that requires +3.3V.
I’m reviving this old post since I may have a need to power the latest Dash 1.1 with 3.3 V directly.
Is that possible per The Dukester’s comments above?
Show me the right path, O Wise Ones.
Here’s a bump, plus a new question!
Looking to power the Dash (v1.1) directly from 3.3V source. Can this be done? Jumper settings? Resistor removal?
How much tolerance is on the 3.3V requirement?
To do that on the Dash 1.1 you would first put the charger into the No Battery position. This is assuming you are not using a battery in this configuration. Connect your 3.3V source to the USB_5V pin, L01. An input voltage down to 3.0V will probably still work. Now the trick is how much current is available. The number we came up with that should work in all situations is 3.5A. That’s a lot, but that is leaving a lot of tolerance for the modem. It may work with a smaller current supply, but there may be situations where the modem is affected. No resistor modifications are needed on the Dash 1.1.
Superb, thanks! Gives me exactly what I need. I’ll give you feedback if I implement.
New follow-up question: Any issue with powering via 3.3V on the battery connector vs. USB (assuming battery connector powered with jumper in battery position)? I was poking around the data sheet, and I see that the USB calls for 4.5 - 5.5V; the battery port seems more range tolerant, looking for 2.2 - 4.4V. Not looking for any kind of magic / ironclad answer; just trying to understand how the Dash works in one scenario vs. the other. (I did have a look at the block diagrams in the docs; my thought (based on jumpers available) is that maybe these are still for Dash 1.0).
I did get the Dash working via USB @ 3.3 (or so) V, but as you suggested, the modemed seemed a bit wonky at that level.
The jumper in battery position enables the charger, which is not what you want here. With the jumper in USB position, the USB_5V and VBATT are the same line. So if you want to use the VBATT pin, removing the jumper completely is probably the way to go. But you shouldn’t see a difference operationally.
Ah!! Got it! That explains it. Thanks, Erik.