Stuart Knight

iTrader: (2)

This is what I currently have fitted to my bike as a gear position indicator, but I would like to change it a single led numerice 7 segment indicator. anybody able to provide a simple (layman terms) diagram (preferably with maplin/rs part numbers for what I need. I have found the display and looked at various bcd/latch controllers but they only have 4 inputs and I need 7. Also input voltages need to be cut down to 1.5V from 12 for most of these controllers. Anybody able to help?

Stuart Knight

iTrader: (2)

Bugger, won't let me edit the original post.

Anyway this is the existing setup

minty

iTrader: (1)

Could you do something like this for a Scooby too it would be wuite cool ???

WRC style with a small gear indicator in the dash ??

paul_davies

here is a link for a seven segment driver and BCD decoder,

http://www.onsemi.com/pub/Collateral/MC14511B-D.PDF (sorry no clicky)

But you will have to use some other logic gates to get to true binary, I may work this out but no promisies as I'm still trying to find the time to finish my charge temp/Auto water spray off (that I started the other side of the summer) but now it's cold it doesn't matter that much and this looks more fun. Just one question, How did you mount the switches?

Hope this helps

Paul

Stuart Knight

iTrader: (2)

Paul, The "switch" is a rotary arrangement of pins, which when the gear selector drum turns, contacts each pin sequentially and earths them out. There is a live feed to each LED and the switch just grounds one out at a time.

Stuart

David_Wallis

I was going to say look at BCD / 7 Segment display drivers..

but you would have to get bcd input..

David

paul_davies

I have found a simple but effective answer by just diode "or-ing" the inputs from the switches to the 7 segment LED, I'll bring some scribles with me to the wycombe meet tonight

dr_ming

Beat me to it. This is the easiest method by a long way, all you need is a fist-full of diodes (use 1N4148, or equivalent), and current a limiting resistor for each segment on the 7-seg display.

Assuming a red/yellow or green display, about 560 ohms will give you an LED current of ~20mA, which is the max continuous current for most LEDs. For a blue display, use 470 ohms. The resistors need to be 1/4 or 1/2 watt.

Don't use one common resistor for all segments, or the brightness of the segments will vary depending on how many are lit (and they will be different, due to mis-matches in the Vf for each segment).

From you switch circuit, you will need a common anode display (all the LED +ve connections commoned together, -ve connections separate).

[Edited by dr_ming - 10/10/2003 1:46:08 PM]

Stuart Knight

iTrader: (2)

dr_ling and paul,

Thanks very much, between you I think I've sen the light. Order some bits off maplins, so will be busy soldering next week. I'll let you know if I get it working.

Stuart