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Sequential (CHASE) Turn Signals

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hi Pete,
Your having a late night....
Problem with the Darlington being driven by a 5V signal source is that its not possible to get at the emitter more than [5V - Vbe] drop, about 5V -1.4V = 3.6 across the LED's.

Ref: my edit in post #4

EDIT:
This is a darlington option using a NPN type, note the led's are ON when the picaxe output is low.

This will give ~ 10.5V across the leds.
 

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Yes i should have known that.

In your schematic could i just use a low output to drive Q3 from the picaxe and not use Q1.

Or is Q2 really needed and not have a darlington output.

Its not quite midnight here yet so its not over late for me, but i should be on the bench finishing some of my own projects and not dancing on the keyboard here.
O-well we all need a little time out now and then.
I have a habit of lying in bed and pondering over problems and often better to solve them and then actually sleep better.

You have almost convinced me a fet might be easier and a lower component count too.

I had considered just sticking a L293D motor driver chip in circuit and using that as a driver but only get 4 outputs and i need 6, although it would have kept it compact and tidy.

Pete.
 
hi Pete,
Driving Q3 direct from the picaxe, would put 12V on the pixaxe pin, when the pin goes high.....

Catch you tomorrow...

EDIT:
This is a useful driver IC..
see pdf.
 

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Thats a neat driver for high side applications, but i am doubtful if 120ma is enough.
The other thing is i have access to a wide range of components but Mike (OP) might not be able to source dedicated devices as easy in the States.

When i thought about the question regarding Q3 i did realize why you had it in there, and is what my original problem was with driving the high side with 5v logic.

Might not get much of a chance tomorrow night to discuss this further but will get back in the next few days.

Thanks so far Eric.

Pete.
 
Thats a neat driver for high side applications, but i am doubtful if 120ma is enough.
The other thing is i have access to a wide range of components but Mike (OP) might not be able to source dedicated devices as easy in the States.

When i thought about the question regarding Q3 i did realize why you had it in there, and is what my original problem was with driving the high side with 5v logic.

Might not get much of a chance tomorrow night to discuss this further but will get back in the next few days.

Thanks so far Eric.

Pete.

Hi Pete,

This option sets the leds on when the picaxe pin is high

EDIT:
If the OP can get a 74LS06 IC, this will reduce the component count.
Ref image #2
 

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Thanks old mate,

I do rather the fet circuit now and this all needs to fit on a tiny board apparently, so a lesser component count the better.

Waiting on a visitor to drop off a controller from a truck for urgent repairs tonight so wont be on the nerdy net much today.

Will get back to you in the comming days.

Pete.
 
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