Power Consumption AXE134Y 20*4OLED?

hippy

Technical Support
Staff member
The 16 x 2 OLED display seems to draw less than 1mA when blank and about 34uA per pixel so that would suggest around 100mA if all pixels are on for a 20 x 4.
 

Hendriks

Member
I happen to be working on a 20x4 OLED right now.
Just measured 48mA when in operation, or 38mA after a Hide Display (serout LCD,N2400,(254,8)) command.
 

nick12ab

Senior Member
I happen to be working on a 20x4 OLED right now.
Just measured 48mA when in operation, or 38mA after a Hide Display (serout LCD,N2400,(254,8)) command.
That seems abnormally high - current should be very low when the display is off. Does the current consumption drop considerably if the PICAXE-18M2 is removed from the AXE133 PCB or not?
 

Hendriks

Member
Having all characters lit or not changes current from 42 to 45 mA.
After disconnecting the AXE134Y the current drops to 570 uA
 
Thanks a lot for your quick replies guys!
I can confirm that current drops only about 3.5mA from a screen with a lot of characters to a blank screen. In my case from 56mA to 52.5mA.
When I remove the PICAXE-18M2 the current drops to 40mA.
 

john2051

New Member
Hi, I dont know what the others think, but I would check for short circuits.
Was this ready built, or the kit?

regards john
 

Hendriks

Member
I was measuring the current at the source, so PICAXE and AXE134 together.
After disconnecting the AXE134 I measured 570uA for the 08M2 only.
 
I checked again for shorts but without success.

Current on the blank AXE 134Y was 54mA.
By the way: measured current on a 16*2 (AXE 133Y) was only 9mA...quite a difference!
Maybe there is still a short somewhere on the 134Y...it would be great if somebody else could verify my measurement.
Thanks!
 

Hendriks

Member
At 4.80 Volt, the AXE134Y draws 47.6mA (displaying 4 rows of "88888888888888888888"). Current through AXE134 only, no PICAXE connected.
After a serout LCD,N2400,(254,12) 'Hide' command the display still draws 32.6mA.
 
At 4.88V, my AXE134Y draws 56,6mA (displaying 4 rows of "88888888888888888888").
After a serout N2400_16,(254,8) 'Hide' command the display draws 42mA.

However, the oscilloscope shows a pulsed signal: minpeak=20mA/maxpeak=120mA/f=15kHz So i think the difference in our measurement might just be averaging-error from our ampmeters.
But I am still a bit worried about how much current the OLED actually needs....isn't it advertised for using less power than the LCD?
 

nick12ab

Senior Member
At 4.80 Volt, the AXE134Y draws 47.6mA (displaying 4 rows of "88888888888888888888"). Current through AXE134 only, no PICAXE connected.
After a serout LCD,N2400,(254,12) 'Hide' command the display still draws 32.6mA.
Have you removed the PICAXE-18M2 from the AXE133 PCB? This is to find out if the abnormal current draw is coming from the PICAXE-18M2 on the AXE133 PCB or OLED.
 

hippy

Technical Support
Staff member
There seems to be two issues here -

1) Current draw seems very high when the display is blank

2) Current draw seems to increase far less than expected as pixels are lit up

That is at odds with a 16 x 2 display which has low draw when the display is blanked and increases linearly as pixels are lit up. It may be there is something different about a 20 x 4 display but unfortunately I do not have one to hand to test.

When I measured the 16 x 2 I simply looked at what current draw the bench supply was showing. Measured with display off and all pixels on, calculated the effective draw per pixel and checked the draw with fewer pixels on to check it seemed linear as pixels were turned on. When I get a chance I'll re-test my display.
 

Hendriks

Member
Have you removed the PICAXE-18M2 from the AXE133 PCB?
Yes. Without the 18M2 current drops by 4mA.
BTW this concerns the AXE134Y.

My measurement was a little too high because I still had the RS232 download cable connected which is a bad habit. (When I disconnected the GND lead from the power supply, the AXE134 and PICAXE board kept on running through the download cable!)

So at 4.80Volts:
After 'Clear' (254,1) current = 45.20mA
After '80x"8"' current = 48.20mA
Then 'Hide' (254,8) current = 33.20mA
Then 'Restore' (254,12) current = 48.20mA
Then 'Clear' (254,1) current = 45.20

With the 18M2 removed from the AXE134, current = 29.10mA

However, the oscilloscope shows a pulsed signal: minpeak=20mA/maxpeak=120mA/f=15kHz
I also had a nasty 15kHz signal when measured over the amp meter. A 470uF capacitor right at the AXE134 board removed most of it.
 

nick12ab

Senior Member
Yes. Without the 18M2 current drops by 4mA.
BTW this concerns the AXE134Y.
The PCB with the 18M2 on it has 'AXE133' printed on it and the Winstar OLED does not so I called it that so that you can tell exactly which PCB I'm referring too (as both could be 'AXE134Y PCBs').

So if the abnormal current draw happens when all the PICAXEs (and other ICs) are removed then the OLED must be defective. Does the black blob on the Winstar OLED PCB get warm?
 
Hmm...it seems we are not too far of - at least in your case Hendriks. Maybe it's just tolerance in my case...The datasheet does not mention min/max for the current though.
I measured again with another Ampmeter but I get the same results. Also adding a 470uF Capacitor does not change things significantly.
Current is 38mA when I remove the 18M2 from the AXE133.
It would be great if somebody else could verify-thanks.
 

g6ejd

Senior Member
Is this level (38mA) a problem for you? There is little you can do other than accept that 43mA as it says on the data sheet is the supply current for this display. There may be a strobe input to the display, which you can feed with a variable mark-space square wave, but somehow I doubt it...
 

Hendriks

Member
To make it a little more complicated...according to the datasheet, the typical supply current of a 16x2 oled (Winstar WEH001602E) is 30mA....
 

hippy

Technical Support
Staff member
To make it a little more complicated...according to the datasheet, the typical supply current of a 16x2 oled (Winstar WEH001602E) is 30mA....
In the datasheet for the 16 x 2 I have that's further clarified with ...

Brightness(nits) / Power consumption(measured with random texts)
125(typical) / 150mW(5V*30mA)

When random texts pattern is running, averagely, at any instance, about 1/2 of pixels will be
on.
I have just re-run my tests on an AXE091 plus AXE133Y. The base current is high because there are a number of unrelated circuits powered. At 5V ...

Base current, no OLED connected : 29mA
Display Blanked : 35mA
One line all pixels on : 52mA
Two lines all pixels on : 69mA

Draw for OLED display itself is 35mA - 29mA = 6mA

Draw for one line all pixels on is 52mA - 35mA = 17mA
Draw for two lines all pixels on is 69mA - 35mA = 34mA

That seems to confirm that the display draws about 6mA and each pixel lit adds linearly to the current draw, and that each pixel draws 17mA / (16*5*7) ~= 30uA

At 3.3V ...

Base current, no OLED connected : 17mA
Display Blanked : 21mA
One line all pixels on : 39mA
Two lines all pixels on : 46mA

Draw for OLED display itself is 21mA - 17mA = 4mA

Draw for one line all pixels on is 39mA - 21mA = 18mA
Draw for two lines all pixels on is 46mA - 21mA = 25mA

Roughly about the same as at 5V.

Code:
#Picaxe 20M2
#No_Data

Symbol LCD = C.0

Pause 1000
SerOut LCD, N2400, (254, $40, $1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F )
Do
  Gosub Blank    : Pause 5000
  Gosub OneLine  : Pause 5000
  Gosub TwoLine  : Pause 5000
Loop

Blank:
  SerOut LCD, N2400, ( 254, 1 )
  Return

OneLine:
  SerOut LCD, N2400, ( 254, $80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 )
  Return

TwoLine:
  SerOut LCD, N2400, ( 254, $C0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 )
  Return
 

Hendriks

Member
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