PIC Carrier Board
At the end of this page, you will find a .DIP file that contains the PCB foil in DipTrace format. You can download a freeware version of DipTrace from here that will allow you to edit or print the foil to make your own PCBs.
This carrier board requires 9 components, an IC socket, some turned pin connectors, 2 x turned pin sockets and a 6-way molex connector, and the PCB of course.
If you're in the UK, you can get the parts from Rapid Electronics.
Qty Part Number Description Rapid Part Number
2 C1 & C2 15pf (SMD) 0805 71-1305 (Supplied in packs of 100)
2 C3 & C4 100pf (SMD) 0805 71-1325 (Supplied in packs of 100)
1 C5 100nf (SMD) 0805 71-1400 (Supplied in packs of 100)
1 R1 100R (SMD) 0805 72-0590 (Supplied in packs of 100)
1 R2 1.5K (SMD) 0805 72-0807 (Supplied in packs of 100)
1 D1 1A 20V Schottky Diode (SMD) *see text 47-0988 (Single)
1 D2 LL4148 Switching Diode (SMD) 47-0910 (Single)
1 SK1 28-pin IC socket 22-0117 (Tube of 17)
1 PLG1 6-way molex header 22-0970 (Single) *see text
1 SK2 Pin Header (only 2 sockets needed) 50-8119 (Single strip of 20 sockets)
1 ----- 2 x 14 Header Pin strips 50-8116 (Single strip of 32 pins)
1 PCB
This carrier board requires 9 components, an IC socket, some turned pin connectors, 2 x turned pin sockets and a 6-way molex connector, and the PCB of course.
If you're in the UK, you can get the parts from Rapid Electronics.
Qty Part Number Description Rapid Part Number
2 C1 & C2 15pf (SMD) 0805 71-1305 (Supplied in packs of 100)
2 C3 & C4 100pf (SMD) 0805 71-1325 (Supplied in packs of 100)
1 C5 100nf (SMD) 0805 71-1400 (Supplied in packs of 100)
1 R1 100R (SMD) 0805 72-0590 (Supplied in packs of 100)
1 R2 1.5K (SMD) 0805 72-0807 (Supplied in packs of 100)
1 D1 1A 20V Schottky Diode (SMD) *see text 47-0988 (Single)
1 D2 LL4148 Switching Diode (SMD) 47-0910 (Single)
1 SK1 28-pin IC socket 22-0117 (Tube of 17)
1 PLG1 6-way molex header 22-0970 (Single) *see text
1 SK2 Pin Header (only 2 sockets needed) 50-8119 (Single strip of 20 sockets)
1 ----- 2 x 14 Header Pin strips 50-8116 (Single strip of 32 pins)
1 PCB
Which version of the carrier board to construct
There are two version of the carrier board with the only different being the ICSP connector and pinout.
The original version of this design was a custom pinout that I've adopted over the years and all my projects use this design. However, I've included a second version of the PCB foil (see file download below) that can be used to create a version of the carrier that will allow direct connection to the socket on a PICKIT2/3.
If you design to build the version of the board, replace PLG1 with a 6 way header as the programmer won't fit correctly over the molex connector.
The original version of this design was a custom pinout that I've adopted over the years and all my projects use this design. However, I've included a second version of the PCB foil (see file download below) that can be used to create a version of the carrier that will allow direct connection to the socket on a PICKIT2/3.
If you design to build the version of the board, replace PLG1 with a 6 way header as the programmer won't fit correctly over the molex connector.
Figure 1. Petri dish (very hand for keeping your parts from vanashing) showing the project parts and reference numbers.
Most of the above parts are supplied in packs. The good news is that they are still fairly inexpensive and the parts are common enough that they will be useful in other projects.
Figure 2. PCB Foil underside of the custom module version (top) and the PICKIT compatable version (bottom), showing the location of the SMD compoennts. Notice the "bar" on D1 and the blue "dot" for D2 that indicate the diode cathodes.
Circuit Description
The circuit is very simple and as such no circuit diagram is needed; you can see from the PCB foil on Figure 2 how the circuit works.
At the centre of the circuit is the socket SK1 for the PIC. Most of the pins from the IC socket are the connected to an adjacent header pin and/or to the 6-way molex connector.
The main exception is the +ve that would usually be connected to pin 20 of the PIC. +ve is picked up from the breadboard, fed via D1 and then back to pin 20 on the PIC socket. This diode prevents the PIC programmer from accidently powering the circuit during programming; this could destroy the programmer. A schottky diode is used to reduce the forward voltage drop as much as possible. If you always intend to run the PIC at it's maxium working voltage, you could replace this diode with a cheaper standard one; i.e. 1N4001.
R1 and D2 ensure that the PIC's MCLR pin is held high during normal operation, but the 1.5K resistance is high enough to allow the PIC programmer to control this pin during programming. D2 prevents the +12v Vpp the PIC programmer supplies during the write cycle from escaping on to the +5v rail and possibly damaging the PIC or any other components on the breadboard. You can still connect the MCLR to a reset switch to ov if required. C1 and C2 are the load capacitors for the crystal, and C3, C4 and R2 help produce a nice clean square wave on the programming pins (27 & 28) during PIC programming. C5 which is soldered directly across the pins where +ve enters the board provides some de-coupling for the PIC. This is BEFORE the diode as to not interfear with the PIC programmer when connected.
Pin 26 is also connected to pin 6 of the molex connector (left blank on the PICKIT version). I often use this pin during project development and debugging to send serial data to my dumb-terminal. Debugging is a dream using this feature.
At the centre of the circuit is the socket SK1 for the PIC. Most of the pins from the IC socket are the connected to an adjacent header pin and/or to the 6-way molex connector.
The main exception is the +ve that would usually be connected to pin 20 of the PIC. +ve is picked up from the breadboard, fed via D1 and then back to pin 20 on the PIC socket. This diode prevents the PIC programmer from accidently powering the circuit during programming; this could destroy the programmer. A schottky diode is used to reduce the forward voltage drop as much as possible. If you always intend to run the PIC at it's maxium working voltage, you could replace this diode with a cheaper standard one; i.e. 1N4001.
R1 and D2 ensure that the PIC's MCLR pin is held high during normal operation, but the 1.5K resistance is high enough to allow the PIC programmer to control this pin during programming. D2 prevents the +12v Vpp the PIC programmer supplies during the write cycle from escaping on to the +5v rail and possibly damaging the PIC or any other components on the breadboard. You can still connect the MCLR to a reset switch to ov if required. C1 and C2 are the load capacitors for the crystal, and C3, C4 and R2 help produce a nice clean square wave on the programming pins (27 & 28) during PIC programming. C5 which is soldered directly across the pins where +ve enters the board provides some de-coupling for the PIC. This is BEFORE the diode as to not interfear with the PIC programmer when connected.
Pin 26 is also connected to pin 6 of the molex connector (left blank on the PICKIT version). I often use this pin during project development and debugging to send serial data to my dumb-terminal. Debugging is a dream using this feature.
Circuit Construction
Construction is straightforward and should commence with the SMD components; Capacitors, resistors and then the two diodes.
If you've never soldered SMD components before, this is an idea first project as all the SMD compoonents are two-pin, and are reasonably tolorant to heat.
The following two video clips show how to solder an SMD resistor and then the power diode.
If you've never soldered SMD components before, this is an idea first project as all the SMD compoonents are two-pin, and are reasonably tolorant to heat.
The following two video clips show how to solder an SMD resistor and then the power diode.
|
|
|
Next solder in the 28-way IC socket, making sure that you insert it the correct way around.
Soldering of the two 14xway pin headers is also quite straight forward, BUT you must make sure they are alligned correctly else the completed module won't fit into a breadboard.
Soldering of the two 14xway pin headers is also quite straight forward, BUT you must make sure they are alligned correctly else the completed module won't fit into a breadboard.
Figure 3. Using a scrap piece of strip-board to make sure the pin strips are correctly spaced.
Insert the two pin-header strips and then place a small scrap of strip-board or matrix board over the pin strips - there needs to be four holes distance between the strips. You can now "carfully" solder each pin-strip in place. It's often simpler to solder the two outermost pins first of each strip, and then check to make sure that everything is aligned correctly. You can then solder the remaining pins.
Next solder in the 2 x single turned-pin sockets for the crystal and lastly, solder in the 6-way molex connecter.
Thats' it... job done.
Next solder in the 2 x single turned-pin sockets for the crystal and lastly, solder in the 6-way molex connecter.
Thats' it... job done.
Figure 4. Completed custom ICSP version module
Figure 5. ICSP connector for the custom version of the carrier board viewed from above.
| pic_carrierv3.dip |