18x starter pack Darlington o/p?

[andyfree]

I have just recieved my first Picaxe, an 18x with the starter PCB. It has the 2803A darlington IC on the board. I have read many posts and looked throught the manauls but can not find what voltage the 2803 IC needs. Does it depend on what you are driving?

I know to connect the 4.5v to G and V+ points parked PIC on the PCB, the other points are marked G and V+ PWR. This is the supply for the 2803.

Can anyone tell me what voltage it should be before I blow it up!
Thanks

 

[hippy]

The ULN2803A doesn't really have a power-supply per se, but you can put up to 30V on V+ PWR but only if you have separated V+ PIC and V+ PWR. Otherwise you may destroy the PICAXE.

You can ignore V+ PWR for now and use the board as is with 4V to 5V applied only to G (0V) and V+ PIC.

 

[westaust55]

Further to what hippy has stated,

The ULN2803 has 8 Darlington transistors in an open collector configuration.
In a simplified concept, think of each input-output as controlling an electronic switch from the output pin to ground.

When an input is driven high by the PICAXE, the corresponding Darlington transistor is turned on and pulls the associated output to ground.
When the PICAXE drives the input low, the "switch" is open and the output is left floating (no connection to ground or Vcc/5V).

As per the PICAXE manual part 3, loads are connected from a supply voltage to the ULN2803 output pins.

The ULN2803 is intended to drive loads which require more current that a PICAXE output can control up to a maximum of 500mA.

try to avoid using the outputs for small signal functions such as driving an LCD module. It is better to connect an LCD module directly from the PICAXE output pins if you can access them conveniently.