OLIMEX© 2012

PIC-IO User's Manual

INTRODUCTION:

PIC-IO board was designed as simple platform which to allow control of appliances and

devices with PIC, the idea was to build something like tiny PLC controller which is possible

to program in C or assembler instead of the weird PLC relay language.

Let’s see what we have on board:

Four High voltage/ High Current relays – with NO-NC-COM contacts available on terminal

block. The relay switching current is rated: 15A/125VAC, 10A/250VAC, 15A/24VDC. Note

that these relays are good for switching resistive loads, but if you have to commutate

inductive loads the relays will wear off quickly due to the sparking when disconnect the

inductive loads (like motors).

Each relay have status LED associated with it so you can easy see which relay is in ON and

which in OFF state.

O1 is connected to RA3 CMP1 and PIC CCP module can be used to generate ON/OFF pulses.

O2-O3-O4 are connected to RA2-RA1-RA0.

Four opto-isolated inputs will allow to detect voltages in range +5-24VDC. Opto-couplers are

fast and switch On/Off for 10 uS, so quick signals could be detected.

!NOTE for owners of MOD-IO prior to revision C1: the above information is correct

only for the opto-isolated couplers – the board is capable to handle up to 22VDC for

them. You need to swap R1, R2, R3, R4 - 330R resistors with 470R ones be able to use

24VDC! This has been fixed in the latest revision as seen in the schematics.

I1 is connected to RA4 and is good for counting as this pin is connected to PIC T0CKI.

I2 is connected to RB0 which is INT and generates interrupts.

I3 is connected to CCP1 and is good for pulse width measurement.

I4 is connected to RB4.

The inputs have status LEDs so easy could be seen which input have voltage. Note that the

optocouplers inverse the levels i.e. when on the input have +5V the PIC pin will read “0” and

vice versa.

Status LED is connected to RB5.

PIC-IO have RS232 connector, but the driver is made by tricky level shifter which uses the

other side RS232 negative levels to generate the PIC-IO levels, so on the other side you must