axe 33b backlight

R

rob nash

Senior Member
hello,
i have put the axe 33b module together able to send text all that side works well. but unsure about how to get the backlight to work i,ve fitted the resistor in the rb for 5v. On page 5 of the manual it states backlight on and of by an external circuit i understand that but i thought A K on the axe 33 board provides this fuction to turn the backlight on or of.
can someone help me get the lights on please rob
 
R

rob nash

Senior Member
thx russbow.
i.ve been looking at that post on and of today cant get my head around it and am looking to use clock feature later on.
wht is the lcd + - above the main header?
anyway thx for the reply rob
 
hippy

hippy

Technical Support
Staff member
For the AXE033 I have with non-backlit display fitted - with the main board and display assembled, placed so the connecting header is up, display facing away, battery facing towards you on the right ....

The mainboard is labelled "14 .... 1 K A" ( written upside down )

The display is labelled "14 .... 1 - +" ( written upside down )

For a backlit display the - and + would connect to the backlight. So I would imagine you need to add two extra links between the boards to connect K to - and A to +, fit RB and that's it.
 
R

rob nash

Senior Member
hi hippy,
i follow what you saying and i,ve soldered pins from the mainboard K A which are then soldered to 15,16 of the display which i thought would do the job but am also having trouble finding an program example which would light the display.
just to be clear am looking at the board "battery facing me" i see two holes left of the battery k and A then link A to display - and k to the display + ?.
thx rob
 
hippy

hippy

Technical Support
Staff member
I think that's the way it works and then you've got a power route from the main board to the display. After that you have to supply backlight power to the bottom far left solder pads viewed with the same orientation as before. These pads are described in AXE033.PDF page 5.

As for a program example; you need something to switch power to those molex pin connectors. A high-side switch and a HIGH or LOW from a PICAXE pin controlling it -- This is what is meant by the backlight is controlled by an external circuit; you have to provide that circuit, or wire it so the backlight is permanently on or off.
 
W

westaust55

Moderator
To have your PICAXE control the backlight you can use one of the PICAXE outputs together with a transistor, a resistor or two and if you want adjustment a trim pot.

The AXE033 datasheet suggests a resistor of the order of 5.6 Ohms at position RB on the circuit board.
For some LCD modules I have which have an onboard 8 Ohm resistor, I have also added a 100 Ohm multi-turn trim pot in series and find that a further resistance of the order of 10 Ohms can be used. It all depends how bright you want the back light.

For a possible circuit have a look at just the backlight part of the schematic diagram I posted in post 3 here:
http://www.picaxeforum.co.uk/showthread.php?t=13900
 
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