-5v to 5v into 0v to 3.3v ...

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i have minelab sovereign gt metal detector has target id meter.

the meter lcd display @ times hard read , quite basic.

i'm looking @ creating new 1 scratch oled display , bit of functionality.

there little info on wiring figured since lcd powered detector , gets target id value must possible arduino powered , read value.

normally 4 wires go detector coil. digital meter 5 come detector , 4 leave digital meter has cable used connect meter wire. 1 tid or target id straight detector has (after using multi-meter) -5v +5v correspond directly values on meter.

i pulled id meter apart , did testing/investigation.

it seems 4 wires leave 2 pairs make 2 coils. voltage in these fluctuated quite bit , small.

there small circuit board between 5 incoming wires , lcd screen , understand does... not how.

basically somehow creates stable 8.75v lcd runs off , signal seems 0 0.5v (instead of original -5 +5v) feeds din pin on it.

as experiment able power arduino uno detector using 8.75v on barrel connector. expected... reading value it's input gave 0 full range small.

the circuit has pot allows input signal tuned before coming in.

it has 4 diodes i'd guess turn +ve , -ve signals +ve.

has 3 capacitors i'd guessing allow small device powered. (100nf @25v).

assuming can copy circuit (as it's 1 sided , handful of components) should able power arduino.

i not sure how scale -5v +5v either 0v 5v or 0v 3.3v.

for 5v arduino need divide input voltage 2 , shift +2.5v , similar if go 3.3v mcu.

i'd attach copy of circuit in meter... except brother has borrowed detector week.


link below shows how external multimeter can connected , used. want able use oled, not have external batteries , have few buttons allow options.

http://dcdetec.com/meter/meter.htm


i understand how voltage divider works , fine calculations... it's shifting that's throwing me. if 0v 10v scale 0v 5v or 0 3.3v easily.

to convert  -5 +5  0 +5 easy

just 2 equal resistors in series. - 10k. 1 end  of r1 +5, junction r1,r2 output, low end r2 input signal.

to convert 0.3.3v,  3 resistors :r1  3.3, junction out, r2 lowerend  input before

but upper resistor r1 (to +3.3) 10k, lower r2 15k.  add r3 30k junction ground

good 'ole kirchoff!

regards 

allan


Arduino Forum > Using Arduino > General Electronics > -5v to 5v into 0v to 3.3v ...


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