@kenbarbi The points you asked about will show you 5V, but those pins are post-PMIC, so it will show a regulated 5V output. I just measured it at 5.02V.
The pins on the microUSB connector will show you exactly what is coming into the board before being sent through a power management IC. Even some fat probes from a generic multimeter should be able to pick up the outside pins on the microUSB connector. When I measure at that location, I get 5.12V.
Oh OK - - good to know. Right now, I have stripped back a USB cable exposing my + and - so I can measure it in its native mode! Ken
Second request, please. What are the limits of input to the PMIC? We know that at 4.9vdc it fails, but what is the high limit, per the manufacturerās specifications? Could a person get by with a 6vdc power supply? Thanks.
Just a word of clarification on 5.25 vdc 2.4 amp USB power supplies from one company that sells them for about $8 - -
The PMIC used in Dreamcatcher is the Allwinner AXP209. Here is a link to the datasheet.
But there is another component in there which doesnāt like more than 5.5V.
I think these devices are at most 5.25 vdc. Iām going to try one to see what happens. Ken
Thanks for the information, This is what I was fishing for. So would it be safe to assume that we could safely apply up to a measured 5.4 volts dc to the micro usb connector on the Dreamcatcher under most conditions without causing damage to any circuitry? If so, does this apply to all the Dreamcatchers from 3.02Q to 3.05?
I do not advise you to go much higher than standard USB output.
Hereās a picture of what you mean. I think this measurement is important for other Forum members who are experiencing Dreamcatcher start up problems to measure their input voltage. Iām adding it to the Userās Guides too - - Ken
I received and installed a $7 Regulated Raspberry Pi Power Supply from Amazon to drive the Dreamcatcher - -
Here are its specs:
Hopefully Iāll never have another failure! Ken
Checking various sources, then, USB standard is 5.0 Ā± 5% = 4.75 to 5.25v, so knowing the problems with the Dreamcatcher that begin at 5.0 and lower, the limits for the Dreamcatcher are 5.0 to 5.25 volts dc?
Yes, 5.0V to 5.25V is safe.
@Syed, is the 5volt bus the same for the larger, USB Type A connector for the WiFi dongle as it is on the micro USB connector? It may be easier to probe the connections there?
The USB-A is regulated and does not come directly from the microUSB connector.
Hereās the Dreamcatcher Schematic p1p2.pdf (136.6 KB) .
Thank you for the schematic. As it appears that manufacturers of power warts seem to be stuck at the USB standard of 4.75 to 5.25 as being ok, is it possible that in future iterations of the Dreamcatcher, in order to come in line with the āUSB standardā, of using hardware that is not so voltage sensitive, as in possibly just let the unit operate as low as 4.70, and a swing up to 5.30, vice exactly at 5.0 to 5.25, which is actually not up to the USB standard of Ā± .05%. I know that custom equipment manufacturers donāt have to meet that standard, but it sure would make working with the rest of the market much more convenient. I know from experience in power provisioning that d-d conversion (which you do use in the Dreamcatcher) can be arranged in those tolerances to provide a steady supply within the device rather than depending on the customer (Joe or Tom average ham radio operator, for example) to find a device that brings the internal supply within tighter specifications (5.0 to 5.25). It would seem that most of the issues we have had to overcome were related to this, from version 3.02Q to present with the 3.05, and the rest of the unit has worked beautifully once the 5.0v issue is overcome. In relation to cost, (which I know you are conscious of, in larger quantities than we even deal with), it has cost probably half of your Dreamcatcher customers the price of at least one wall wart per Dreamcatcher sold since the 3.02Q. Perhaps the simple solution would be as @kenbarbi Ken has stated, raise the price by $8 US and provide a regulated power supply with each unit soldā¦ The little $2 buck converters could probably be implemented at the cost of 3/4 of a square inch of circuit board, and you could provision it with a coaxial connector supplying from 6.0 to 26.0 volts.
