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This question already has an answer here:

I am trying to connect the MMA5452Q accelerometer to arduino on 5V (later it will be substituted with attiny85, hence the 5V voltage). It works just fine when i supply arduino's 3.3V. When i try the 5V supply and split it with resistors (R1, R2, R3) the accelerometer does not work any more. I measured the voltage of the circuit. It is 1.1V but MMA5452Q requires 1.6-3.3V. I was trying different combinations but i am afraid that doing it blindly at some point I will just burn the chip. What is going on here? Could anyone tell me how to connect it so the voltage maches? (And how to calculate this - so I dont need to ask every time :) )

P.S. R5 and R4 are pull ups required by accelerometer's documentation. Works when the circuit is powered with 3.3V

P.S.S. I am not an electrical engineer. I am hoping that this question is not terribly stupid.

schematic

simulate this circuit – Schematic created using CircuitLab

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marked as duplicate by Marcus Müller, DoxyLover, uint128_t, Dmitry Grigoryev, laptop2d Apr 7 '17 at 16:02

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    \$\begingroup\$ See When would I use a voltage regulator vs voltage divider? \$\endgroup\$ – CL. Apr 6 '17 at 9:13
  • \$\begingroup\$ Yep. You're using a loaded voltage divider. This doesn't work. \$\endgroup\$ – Marcus Müller Apr 6 '17 at 9:14
  • \$\begingroup\$ ahh i see... so there is no way around and i need to buy the voltage regulator...? \$\endgroup\$ – Chris Apr 6 '17 at 9:15
  • \$\begingroup\$ @Chris would definitely the easiest way to go. These things do what you need and cost cents. \$\endgroup\$ – Marcus Müller Apr 6 '17 at 9:41
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No need for a regulator. Buffer with an opamp. Have OUT connected to IN- and your +3.3 from the divider connected to IN+. Remove other connections to the divider. Run the opamp from the +5V rail. Use the opamp OUT to run the +3.3V rail with the pull resistors etc. Make sure the opamp can supply the current required by the accelerometer.

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    \$\begingroup\$ Surely this is larger and more complicated than just buying a regulator? \$\endgroup\$ – pjc50 Apr 6 '17 at 9:35
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    \$\begingroup\$ Don't mean to be mean, but: an Opamp with a voltage divider is a voltage regulator, and nothing else. Just a relatively complicated, uncompensated, untested and potentially expensive one. \$\endgroup\$ – Marcus Müller Apr 6 '17 at 9:35
  • \$\begingroup\$ @pjc hehe, collision \$\endgroup\$ – Marcus Müller Apr 6 '17 at 9:36
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    \$\begingroup\$ It's a fair option and, if you have a spare op-amp from a multipack already on-board, a better one than an extra regulator. It can't be called a bad answer. \$\endgroup\$ – TonyM Apr 6 '17 at 9:56
  • \$\begingroup\$ I think in terms of getting things working for OP my solution was the better option. It's not like he's designing for HVM. Sure, wait till you can buy a voltage regulator, you guys must just have more free time than me. \$\endgroup\$ – Tim Mottram Apr 6 '17 at 11:49

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