ESP8266 Community Forum

- Mon Jan 11, 2016 9:46 am #38503 Looking at the spec of L293D, VCC1 can be as high as 60mA, but it still manageable with a zener diode, it is the power resistor connected to the zener that will suffer most, depending of your input power supply is 24V. So, choose proper wattage for this resistor.

- Wed Jan 13, 2016 8:53 am #38675 with a 56ohm resistor seems work with 24v and 12v...
but now i need to try with 9v like power source. With a zener 6,8v 1,3W i have only 10mA , so probably it doesn't work.
In this situation , using a zener, there is not the right resistor that can work with 9v and 24v ....
any idea? Maybe i need to use a voltage regulator that can use different voltages sources
thanks for your precious support
Mirko

- Wed Jan 13, 2016 9:11 am #38676 if this is right , i can manage with 22ohm resistor. The problem is the W of the 24V

V zener ohm W mA
9 6,8 22 0,22 70
12 6,8 22,12765957 1,222 205
24 6,8 22,05128205 13,416 750

about 14W if the source voltage is 24v (that really is more or less 27). But if the l293d use only 60mA that is 8%, i have 14*0,08 ??? (=1,12W?)

- Wed Jan 13, 2016 10:22 am #38682 I'm not following you in all your calculations ...
If your input is 24V, the resistor than need to drop voltage of 17.2V at 60mA, that make the resistor value is 17.2V/0.06A=286.6ohms, and this resistor need to dissipate 17.2V*0.06A=1.032W