ESP8266 Community Forum

- Thu Feb 05, 2015 12:17 pm #9070 I'm just designing a single-sided ESP-12/ ESP-07 breadboard adapter PCB which will be easy to etch for anyone who loves to play with the ESP8266 on a breadboard like me.

Features are:

Fits ESP-12 and ESP-07 module
Single-sided self-etchable design
All parts are SMD
Breadboard-style - one row on each side accessible
Vin >4.5V (max. 7V) input possible with 3V3 onboard voltage regulator (with two capacitors 10µF)
Power-indicator LED
(Schottky-) Diode as reverse polarity input protection possible (solder 0 Ohm resistor or just connect the two pads for no protection)
RST, CH_PD, GPIO0 with 4k7 pull-up resistors on board (resistors can be omitted if remote access of those GPIOs is needed)
GPIO15 with 4k7 pull-down (see above)
Tactile switch connected to GPIO0 to get into flash mode
Single post for 3.3V output near voltage regulator

This is the actual revision 1.0 - improved for:

Antenna part now protruding the PCB (no traces below antenna)
Wider traces
Schottky diode for reverse polarity protection
2x 10µF ceramic caps for input/ output of AMS1117
Single post for 3.3V output near voltage regulator

markbee

Last edited by markbee on Sun Feb 22, 2015 12:16 am, edited 8 times in total.

Electronics blog http://lookmanowire.blogspot.com

- Thu Feb 05, 2015 12:40 pm #9074 This is very nice. Just the essentials: LDO regulator, flashing switch, 2.54 mm pin spacing. I have only one concern--do you think the traces under the antenna will affect its impedance or radiation pattern? I've always avoided putting either conductors or additional dielectric underneath a PCB antenna.

- Fri Feb 06, 2015 3:33 am #9114 Yes, good point. I will leave the area free in the next revision ( I had no connection problems though with the beta board).

markbee

This is very nice. Just the essentials: LDO regulator, flashing switch, 2.54 mm pin spacing. I have only one concern--do you think the traces under the antenna will affect its impedance or radiation pattern? I've always avoided putting either conductors or additional dielectric underneath a PCB antenna.

Electronics blog http://lookmanowire.blogspot.com

- Fri Feb 06, 2015 4:24 am #9115 The traces look a bit thin to me, it might be a good idea to make them wider (esp. the power traces).
I would also rotate the ESP-12 by 180° and put the button on the other side, where the LDO is. That way you can mount the ESP, so that there's no PCB underneath (eliminating any risk that your board might affect antenna performance).
You also might want to add a reset button, for easier flashing and I don't see much need for that power LED you added, since the ESP-12 already has one (or doesn't it? there is a LED mounted at least).
As for your protection diode: the diode will typically drop about 0.6V (depending on the actual diode used and the current draw). With a 5V input, that will drop your input down to 4.4V, but the LDO has dropout voltage of about 1.2V. While I like the idea of the reverse polarity protection, a simple diode is not ideal in this situation. Using a MosFET would be better: http://hackaday.com/2011/12/06/reverse- ... h-a-p-fet/ (you can also use a cheaper n-FET, when you put in in the ground line).