Best technique for supplying different voltages from one battery source
Best technique for supplying different voltages from one battery source
(OP)
I've got an Arduino that I want to send 9 volts to and a electromagnet I want to sent 13 volts to. The battery source is a 14.8v lipo. I have a handful of step-down buck converters. It doesn't seem elegant to use 2 step-downs to deliver the different voltages, but this is the first time I've run across this situation. Would this be an appropriate solution?





RE: Best technique for supplying different voltages from one battery source
Or you could put a resistor in series with your electromagnet from the battery for approx 13V.
Z
RE: Best technique for supplying different voltages from one battery source
Keith Cress
kcress - http://www.flaminsystems.com
RE: Best technique for supplying different voltages from one battery source
RE: Best technique for supplying different voltages from one battery source
RE: Best technique for supplying different voltages from one battery source
RE: Best technique for supplying different voltages from one battery source
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RE: Best technique for supplying different voltages from one battery source
For the 9V source I would run a 7808 linear regulator. The on board 5V regulator needs just that to be stable. A common 7805 can be adjusted up with two resistors to obtain that. Never power anything external with the on board 5V except a couple LED. If more power is needed use a external 5V supply.
RE: Best technique for supplying different voltages from one battery source
In the case of an electromagnet, the current is what matters.
RE: Best technique for supplying different voltages from one battery source
// PWM RELAY DRIVER SECTION PIN #3
// PWM relay output will reduce power consumption of relay
if (rly == 0) PWM3 = 0;
// set PWM value to zero if relay should be off.
// DECREMENT PWM VALUE EACH LOOP IF RELAY ON
if (PWM3 >125) PWM3 = PWM3 - 1;
// decrement PWM3 till it reaches minimum value
// reliable operation can often be 40%
// TURN PWM RELAY ON BY SETTING INITIAL VALUE
if (PWM3 == 0 && rly == 1) PWM3 = 255;
// when relay first turns on set PWM3 to maximum value
// prior state of relay has to be off in order to set this value
// this could also be used to power a 12V relay from a 24V source
// THIS OUTPUTS THE PWM SIGNAL TO PIN #3
analogWrite(3,PWM3);
// sets status of PWM3 RELAY output pin #3
// PWM values are between 0 and 255
The on board regulator power should be isolated with a diode and large electrolytic capacitor. I had one system that drew 125A off battery. When the battery was a little weak it would sometimes reset the processor from under voltage drop out. The diode would prevent drawing power from capacitor and the processor would br powered by the cap durring this period.
RE: Best technique for supplying different voltages from one battery source
I don't.
Keep it simple.
Benta.
RE: Best technique for supplying different voltages from one battery source
RE: Best technique for supplying different voltages from one battery source
RE: Best technique for supplying different voltages from one battery source
Your nominal 14.8 volt battery sounds like it has 4 cells. The typical cell voltage for common lithium batteries is 3.7 volts, times four gives 14.8.
A fully charge cell is usually 4.2 volts (there are chemistry variations that range up to 4.35 volts or so).
A completely discharged cell will have a voltage around 3.0 volts, and the cell impedance will increase, so under load the output voltage will be lower than expected. And discharging below a couple of volts or so will permanently damage the cell, so have some sort of low voltage cut-off.
So your battery voltage will range from something like 12 volts up to 16.8 volts, so to truly generate 13 volts requires a boost-buck converter.
Sure, the electromagnet will work at 12 volts with only a slight degradation, but in general, always design your power supply to accommodate the full range of the expected battery voltage. This is tricky when that voltage goes both above and below your output voltage.