10 led bar graph

[Denzel]

I need to use a 10 LED bar graph to gisplay a LPG gas reading. but using a picaxe to control all 10 LEDs is a disguisting waste of outputs...
Are there any solutions to this.

One thing I did consider is to use 10 inputs and make the inputs low and connect the LEDs to the 3v + and the input pin. with a 220 ohm resistor and a signal diode.

are there any ideas that involve using less than 10 of any type of pin??
One wire bus?

Thanks
d-d-denz

 

[moxhamj]

A few options but all require other chips.
HC595 serial to parallel chips. Can put two in series to get 16 outputs or live with just 8 outputs. Takes 3 pins on a picaxe to drive a HC595.
You could use a LM3914 10 led display and drive it off a voltage created with PWM and a RC filter.
You could go for 2 7segment displays and display as numbers.
You could use an LCD display 16x2 characters and display as solid blocks in a bargraph (least power consumption option).
Plus other options I'm sure.

 

[Denzel]

hmmmm

I thought this much.
using multiple ICs provides lots of opportunities that are more bennificial than an led bar graph so I would probably go for a seven segment display or LCD etc

however..

perhaps I could go up in twos.
That is have two leds for one output thats 5 outputs which is a lot better.

thanks

 

[BCJKiwi]

Have used the LM3914 that the Dr suggests. simple to hook up and provides the current control for the LEDs eliminating the resisitors - just hook it up to a 10 Led Bargraph module.

 

[mholguin]

You could use a LM3914 10 led display and drive it off a voltage created with PWM and a RC filter.

Dr.

Can you please throw me some light on how to implement this part?

Thanks in advanced,

Marino

 

[BeanieBots]

Google, type "LM3914", download datasheet, read.
Same process works for most ICs.
http://cache.national.com/ds/LM/LM3914.pdf (to save you some effort)
Nice chip, does all the hard work for you. Also comes in log version.

 

[marcos.placona]

You can also control up to 8 leds with a max7219, and cascade them to N leds. I've used that with some success.

 

[mholguin]

Google, type "LM3914", download datasheet, read.
Same process works for most ICs.
http://cache.national.com/ds/LM/LM3914.pdf (to save you some effort)
Nice chip, does all the hard work for you. Also comes in log version.

I've used the LM3914 before, what escapes my llittle knowledge is how to use a picaxe with PWM to regulate output voltage.

Hope I made sense now

 

[manuka]

Direct use of the new 20M,with 8 outputs, may well suit => http://www.picaxe.orconhosting.net.nz/20m7segds.gif

 

[BeanieBots]

Using PWM to drive an analogue input is as described by Dr_Acula.
The PWM DUTY (the amount of time high vs the amount of time low) charges/discharges a capacitor which results in an analogue voltage which is the same percentage of the supply voltage as the percentage of the duty.

Having said that, Manuka's suggestion of using a 20M is worth considering. Slightly harder to build (you would need current limit resistors on EACH LED) but much more versatile (you could customise the trip points and illumination patterns).