Can someone check my simple eagle circuit? LCD 1602

This is my little arduino lcd board project. I have triple checked the circuit already. should be problem free, but you never know. so before I go ahead and make the board, can someone help me out here. Check the circuit for me again.

For this arduino, I will be using icsp to upload codes, and use tx and rx pin for switching the lcd backlight and a beeper, and I am using internal crystal.


version 2 uploaded!

version 3 uploaded! checked many time! refined symbols many times!

Main.zip (14.4 KB)

Hi, The problem is that a lot of the forum members do not have Eagle. You should be able to export your file as an image to clipboard.

Tom.... :)

TomGeorge:
Hi,
The problem is that a lot of the forum members do not have Eagle.
You should be able to export your file as an image to clipboard.

Tom… :slight_smile:

thank you. I have re-uploaded an image file.

Nothing jumps out at me as being wrong on a quick look.

Why using NPN in emitter follow configuration to switch the high side, instead of switching the low side?

Are you planning to ever program it over serial, or just ISP? If planning to do serial uploads ,you need a header for that, and a diode between RST and Vcc to keep it from going over Vcc.

I'd run the USB header's data pins out to pads - you can use a few resistors between the data pads and Vcc/Gnd to tell the chargers that there's no data, and to enable higher current supply. There's more info on this online; apple and the world do it differently.

Why using NPN in emitter follow configuration to switch the high side, instead of switching the low side?

Yes, use common emitter as implied here.

Need some decoupling on VCC AVCC AREF.

DrAzzy:
Nothing jumps out at me as being wrong on a quick look.

Why using NPN in emitter follow configuration to switch the high side, instead of switching the low side?

Are you planning to ever program it over serial, or just ISP? If planning to do serial uploads ,you need a header for that, and a diode between RST and Vcc to keep it from going over Vcc.

I’d run the USB header’s data pins out to pads - you can use a few resistors between the data pads and Vcc/Gnd to tell the chargers that there’s no data, and to enable higher current supply. There’s more info on this online; apple and the world do it differently.

This is my first arduino board. I want to just use ISP for uploading for now, later will use ft232r chip. I have a mini-usb there just for the power. is there problem with my npn configuration ? I copy that from another circuit.

also, is it a good idea to add resistors and LEDs to my digital pin headers pin8-pin13? pin13 already has one led. will adding LEDs disable the function of those pins?

arduinomagbit: This is my first arduino board. I want to just use ISP for uploading for now, later will use ft232r chip. I have a mini-usb there just for the power. is there problem with my npn configuration ? I copy that from another circuit.

also, is it a good idea to add resistors and LEDs to my digital pin headers pin8-pin13? pin13 already has one led. will adding LEDs disable the function of those pins?

If you plan to use serial for upload later, you should make a header for an FTDI adapter (the 6-pins in a line with RX, TX, Vcc, Gnd, and DTR, DTR connected to one side of 0.1uf cap, other side of cap connected to reset, and reset needs a diode to Vcc (so that reset line can't go above Vcc, which has sometimes bricked chips by briefly entering HVSP mode when DTR is released).

Don't use an NPN transistor in an emitter follower configuration unless you have a good reason for doing so. The internet is full of people throwing around emitter follower circuits as if they're a good "default" way to switch things with NPN BJT transistors (much worse, people just 1:1 swap the BJT with a MOSFET and post that as viable designs - clearly without having actually tested their own design ;-) )

What you want to do is connect emitter to ground (not + side of load), connect + side of load to the supply voltage, and - side of load to the collector of the transistor, base to R5.

Or use a MOSFET - Source to ground, emitter to - side of load. Gate goes to the IO pin, with a 10k resistor between gate and ground. Optionally, put a small (100 ohm) resistor between gate and IO pin as well (some people get worked up about the very brief pulse of current down the IO line to (dis)charge the gate capacitor, which could for a split second exceed the chip's current rating, and put a little resistor in there - I've never put a resistor in series with my mosfet gates, though, and my stuff works. So take that as you will )

No need for extra LEDs and resistors on those pins, unless you need them for something. When I put LEDs on data lines (which I do only when I need to - say, to visualize when the line is in use), I use 1k-2k resistors - they're still bright enough to see for debug, while having less impact on the voltage while the pin is high. Usually the LEDs won't cause problems, but i err on the side of caution, and use large series resistors.

DrAzzy: If you plan to use serial for upload later, you should make a header for an FTDI adapter (the 6-pins in a line with RX, TX, Vcc, Gnd, and DTR, DTR connected to one side of 0.1uf cap, other side of cap connected to reset, and reset needs a diode to Vcc (so that reset line can't go above Vcc, which has sometimes bricked chips by briefly entering HVSP mode when DTR is released).

Don't use an NPN transistor in an emitter follower configuration unless you have a good reason for doing so. The internet is full of people throwing around emitter follower circuits as if they're a good "default" way to switch things with NPN BJT transistors (much worse, people just 1:1 swap the BJT with a MOSFET and post that as viable designs - clearly without having actually tested their own design ;-) )

What you want to do is connect emitter to ground (not + side of load), connect + side of load to the supply voltage, and - side of load to the collector of the transistor, base to R5.

Or use a MOSFET - Source to ground, emitter to - side of load. Gate goes to the IO pin, with a 10k resistor between gate and ground. Optionally, put a small (100 ohm) resistor between gate and IO pin as well (some people get worked up about the very brief pulse of current down the IO line to (dis)charge the gate capacitor, which could for a split second exceed the chip's current rating, and put a little resistor in there - I've never put a resistor in series with my mosfet gates, though, and my stuff works. So take that as you will )

No need for extra LEDs and resistors on those pins, unless you need them for something. When I put LEDs on data lines (which I do only when I need to - say, to visualize when the line is in use), I use 1k-2k resistors - they're still bright enough to see for debug, while having less impact on the voltage while the pin is high. Usually the LEDs won't cause problems, but i err on the side of caution, and use large series resistors.

okay. I have re-pined the 2 npn, added a fuse, added 5 leds to pin8-12 connected with 1k resistors, and added a decoupling capacitor to the power supply. can you help me check it again. I hope the connected leds to the icsp header won't be a problem when I upload codes to it. It's there just for fun. Leds are fun. I will add FTDI once this first board is up and working. also, is there anything I can add? a voltage regulator is not really required here, since I am planning to run my board using lithium battery.

Bypass caps are usually .1u, not 1u.

db2db: Bypass caps are usually .1u, not 1u.

thank you for pointing this out to me. fixed!!

Did you end up adding a 10k trim pot for the 1602 display?

Don't connect AREF to Vcc. Just a 0.1uF cap from AREF to Gnd. It connects to Vcc internally when selected.

Huh - April 15, guess someone (haloway13) opened an old topic!