Micro Controller Circuit Design and PCB Development
Budget: £250 – £750 GBP
I'm looking for an experienced circuit designer to assist in the development of a functional PCB following correct procedures and best practices.
I will require advice from you as I will only be supplying limited details. You will need to access if any ancillary components are required, such as pull ups/downs, decoupling etc.
The PCB front print is to be kept as small as reasonably possible.
- Brief
This PCB will be used in 2 modes, Master and Slave.
Master
The master will be powered via a 12v regulated DC power supply.
It will also connect an external 12v device (NAYAX) and a 5v (LCD) on I2C.
Slave
The slave will be powered via a 16.8v Li-Ion battery, there will be no external 12v device connected and no LCD display. We require this mode to have a VERY low quiescent current, so this should be your primary focus in this design.
The input voltage range will be between 11.5v and 16.8v. The DC to DC circuit must provide a stable 5v and 12v line. However the 12v will be unused on the slave so if it helps with the quiescent current, there could be a jumper to disable the 12v ?
- Main Components
ATMEGA 328P
NRF24L01
16 Channel Analog Multiplexer (possibly CD74HC4067)
8 bit SIPO register (possibly SN74HC595)
8 way DIP/DIL switch
screw terminal blocks: 1x2 way, 2 x 8 way
- Connections
+NRF24L01 (5v)
Maybe the best option to purchase these devices as pre built boards (see attachment) and have them connect on to the PCB via a 2x4, 8 way header plug.
+CD74HC4067 (5v)
All inputs are PULLED LOW
C0 - C7 = External inputs (8 way screw terminal block, see attachment)
C8 - C16 = DIP/DIL inputs
+SN74HC595 (5v)
Q0 - Q7 = External outputs (8 way screw terminal block, see attachment)
These outputs are driving LED, so could resistors placed on all outputs, or a resistor network.
+8 way DIP/DIL switches
Held low, ACTIVE HIGH
+MCU (5v)
The ATMEGA328, needs to be removeable, so possibly the SPDIP package in a push fit connector.
0 - RX (2 way pin header)
1 - TX (2 way pin header)
2 - NRF24L01 IRQ *
3 - NAYAX IRQ **
4 - CD74HC4067 S0
5 - CD74HC4067 S1
6 - CD74HC4067 S2
7 - CD74HC4067 S3
8 - CD74HC4067 EN
9 - NRF24L01 CE *
10 - NRF24L01 CSN *
11 - NRF24L01 MOSI *
12 - NRF24L01 MISO *
13 - NRF24L01 SCK *
14 - SN74HC595 LATCH (Pull up 5v)
15 - SN74HC595 CLOCK
16 - SN74HC595 DATA
17 - NAYAX EN ** (Pull down GND)
18 - LCD SDA ***
19 - LCD SCL ***
20 - Voltage divider to read input (battery) voltage
21 - CD74HC4067 SIG
* 2x4 8 way female header, to correctly match NRF24L01 pinout (attached)
** Some 4 way connector, requires 12v and GND (possibly male pin header)
*** Some 4 way connector, required 5v and GND (possibly male pin header)
- Power
2 way screw terminal block (see attachment).
Powered from an external Li-Ion battery with a voltage up to 16.8 volts. So there will need to be some circuit to step this down to 5 volts AND 12 volts. NOTE the quiescent current of the DC to DC circuit must be as low as possible.
The input should be protected from reverse polarity.
-Voltage Divider
We need to monitor battery voltage and since the ATMEGA can only cope with 5v you will need to have a voltage divider circuit. See attached document from ChatGPT on this.
I will require advice from you as I will only be supplying limited details. You will need to access if any ancillary components are required, such as pull ups/downs, decoupling etc.
The PCB front print is to be kept as small as reasonably possible.
- Brief
This PCB will be used in 2 modes, Master and Slave.
Master
The master will be powered via a 12v regulated DC power supply.
It will also connect an external 12v device (NAYAX) and a 5v (LCD) on I2C.
Slave
The slave will be powered via a 16.8v Li-Ion battery, there will be no external 12v device connected and no LCD display. We require this mode to have a VERY low quiescent current, so this should be your primary focus in this design.
The input voltage range will be between 11.5v and 16.8v. The DC to DC circuit must provide a stable 5v and 12v line. However the 12v will be unused on the slave so if it helps with the quiescent current, there could be a jumper to disable the 12v ?
- Main Components
ATMEGA 328P
NRF24L01
16 Channel Analog Multiplexer (possibly CD74HC4067)
8 bit SIPO register (possibly SN74HC595)
8 way DIP/DIL switch
screw terminal blocks: 1x2 way, 2 x 8 way
- Connections
+NRF24L01 (5v)
Maybe the best option to purchase these devices as pre built boards (see attachment) and have them connect on to the PCB via a 2x4, 8 way header plug.
+CD74HC4067 (5v)
All inputs are PULLED LOW
C0 - C7 = External inputs (8 way screw terminal block, see attachment)
C8 - C16 = DIP/DIL inputs
+SN74HC595 (5v)
Q0 - Q7 = External outputs (8 way screw terminal block, see attachment)
These outputs are driving LED, so could resistors placed on all outputs, or a resistor network.
+8 way DIP/DIL switches
Held low, ACTIVE HIGH
+MCU (5v)
The ATMEGA328, needs to be removeable, so possibly the SPDIP package in a push fit connector.
0 - RX (2 way pin header)
1 - TX (2 way pin header)
2 - NRF24L01 IRQ *
3 - NAYAX IRQ **
4 - CD74HC4067 S0
5 - CD74HC4067 S1
6 - CD74HC4067 S2
7 - CD74HC4067 S3
8 - CD74HC4067 EN
9 - NRF24L01 CE *
10 - NRF24L01 CSN *
11 - NRF24L01 MOSI *
12 - NRF24L01 MISO *
13 - NRF24L01 SCK *
14 - SN74HC595 LATCH (Pull up 5v)
15 - SN74HC595 CLOCK
16 - SN74HC595 DATA
17 - NAYAX EN ** (Pull down GND)
18 - LCD SDA ***
19 - LCD SCL ***
20 - Voltage divider to read input (battery) voltage
21 - CD74HC4067 SIG
* 2x4 8 way female header, to correctly match NRF24L01 pinout (attached)
** Some 4 way connector, requires 12v and GND (possibly male pin header)
*** Some 4 way connector, required 5v and GND (possibly male pin header)
- Power
2 way screw terminal block (see attachment).
Powered from an external Li-Ion battery with a voltage up to 16.8 volts. So there will need to be some circuit to step this down to 5 volts AND 12 volts. NOTE the quiescent current of the DC to DC circuit must be as low as possible.
The input should be protected from reverse polarity.
-Voltage Divider
We need to monitor battery voltage and since the ATMEGA can only cope with 5v you will need to have a voltage divider circuit. See attached document from ChatGPT on this.