Timeline for 5V to 3.3V for bluetooth module - Is a voltage divider ok?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Nov 28, 2018 at 11:57 | vote | accept | Jeppe Christensen | ||
| Nov 26, 2018 at 16:26 | comment | added | Hearth | @isdi I don't know much about the power demand of wireless communication. Microamps did seem pretty small, though. | |
| Nov 26, 2018 at 16:01 | comment | added | user201365 | @Felthry, Yes, I had to dig down on that eBay page, but there is a line at the bottom "1PCS Bluetooth 4.0 module BLE CC2541 low power NEW HM-11 ", hence my take on it. 90uA -peak- for active Tx/Rx would be pretty impressive, but if it's time-averaged it can be easily achieved, just depends on the usual data length and wake cycle parameters. | |
| Nov 26, 2018 at 1:20 | history | edited | Hearth | CC BY-SA 4.0 |
Change recommendation to a slightly higher current device
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| Nov 26, 2018 at 1:16 | comment | added | Hearth | @isdi I was suspicious of it too, but it says 90μA "working current"... Still, that's just an ebay description, I wouldn't trust anything from that. Perhaps I will change that recommendation from a 10mA regulator to a 25 or 50mA one though. | |
| Nov 26, 2018 at 0:51 | comment | added | user201365 | The microamp rating is most likely when it's sleeping. Typical BLE devices run at around 15-20mA when receiving and transmitting, depending on transmit power output levels (further down it states the active part is a TI cc2541). Since this is 4 orders of magnitude difference you would need some kind of active regulation for power. For -input- signals, resistive dividers should work but watch out for RC rise times vs pin current drive capabilities. Going from the 3.3V level to a 5.0 level can be tricky if the 5V part input(s) are not TTL level compatible. | |
| Nov 25, 2018 at 21:56 | comment | added | Jeppe Christensen | Understood, i will mark it accepted in a couple of hours then. | |
| Nov 25, 2018 at 21:55 | comment | added | Hearth | @JeppeChristensen And please don't mark this as the accepted answer yet! It's recommended that you wait at least a day for other answers to come in, which may be better than mine--but if people see the question already has an accepted answer they're less likely to write their own, possibly better ones. | |
| Nov 25, 2018 at 21:54 | comment | added | Hearth | @JeppeChristensen I couldn't tell you about pull-down resistors but you'll definitely want a voltage divider. Read your datasheets to see what sort of pullup/pulldown you'll need. | |
| Nov 25, 2018 at 21:51 | vote | accept | Jeppe Christensen | ||
| Nov 25, 2018 at 21:56 | |||||
| Nov 25, 2018 at 21:50 | comment | added | Jeppe Christensen | Again, thank you :-) Do you reckon that I need a pull-down resistor and voltage divider for the RX pin - now that the module is 3v3 compatible? | |
| Nov 25, 2018 at 21:41 | history | answered | Hearth | CC BY-SA 4.0 |