Electrical – ESP8266 controlling RC car. Voltage drop, ESP shuts down when I increase motor speed

dc motoresp8266l293dremote control

I am preparing remotely controlled RC car using Android phone and ESP in TCP client/server configuration. I power it using 4x AA 1.2V batteries (2500mAh). The problem occurs when I try to accelerate with more power (max PWM on L293D). ESP-12's LED dims till it shuts down. When I use small PWM rate, I get only dimming, but car works ok.

Some more info:

  • When in idle state – with smartphone connected, ESP has 3.15V. Moving servo lowers it to 3.14, but when I start moving motor with bigger PWM there is a drop even to 2.3V.
  • My motor takes even about 1.4A when it is connected directly to my 4 batteries (5.3V). When using L293D motor has about 0.45A,
  • I am aware that L293D is only capable of giving me 600mA on one channel, but thats why I used bridged configuration (not a big improvement, but it is a little better). But this small output current makes me even more sure, that L293D is quite 'weak' and should not take all energy thats in the circuit.

Here's what I've already tried:

  • Adding capacitors between Vcc & GND of ESP, to give it some energy in 'hard times' – it has really small impact.
  • Using not bridged cofiguration of LD293 in the case if L293 drains 2x more current or is somehow 'overpowered' (this configuration provided below is bridged – I connect inputs and outputs of 2 channels together – as far as I know it is ok)
  • Getting rid of voltage regulator – I connected ESP directly to 3 of 4 of my accumulators (3,90V without a diode, 3,71V with a diode). The same dimming.

Please advise. Maybe I lack some capacitors or protection from noises? I thought about ordering L298, but considering that probably I have to small power efficiency, ordering IC that has bigger output current is not really reasonable.


Best Answer

The ESP chips are notoriously sensitive to power supply voltage droop. You appear to have essentially zero decoupling, filtering, reservoir capacitance for the ESP8266.

Suggest using an isolation diode and a separate "reservoir" capacitor just for the ESP. The diode will keep the dedicated ESP power reservoir capacitor from feeding back into the other parts of the circuit like the power-hungry motors, etc. I would use something in the thousands of uF (as big as the project will allow). As your experiments showed, not clear what that 3.3V regulator is doing for you??