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Topic: External Voltage supply (Read 580 times) previous topic - next topic

Max89

I have some stepper motors to power so I need to use some external voltage source, I chose LM317 circuit from  datasheet and Li-po battery(1700 mAh 25C)
How I can put it into use ?  Positive wire to L293D leg which supply power for stepper motor , negative one to gnd of arduino ?
I tried this but It fail a bit... Where is mistake  ? How to connect them.
I have solution !
But it involves spherical chickens in frictionless vacuum...

Grumpy_Mike

Look at the data sheet and you will see it is more complex than this.
You need a potential divider and decoupling capacitors.

Max89

I know, I build  1.2V-25V voltage  regulator from  typical application section. But I see my mistake right now ....
http://www.ti.com/lit/ds/symlink/lm117.pdf Input voltage should be more or equal 28V. I connected far less ...
I have solution !
But it involves spherical chickens in frictionless vacuum...

Grumpy_Mike

No the input voltage must be a few volts more than the output voltage not more that 28V. That first diagram is for a regulator that goes up to 25V.

Max89

Ok so I had circuit from this diagram except Resistor 240 ohms - I had only 220 ohms so I used it.
It works properly, using a pot I can change voltage. I set it to 3.3V and put positive terminal to leg on L293D corresponding for supplying motor. Negative one to GND of same IC and... nothing. 
I have solution !
But it involves spherical chickens in frictionless vacuum...

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