Surely this should be easy...!

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Thread Starter

Thorfinn

Joined May 23, 2012
3
All I need is a circuit that, when 12V is applied, passes 12V at about 0.25A to a miniature bulb, then after about 5 seconds, cuts power to the load and only resets at the next power down/power up cycle.

It is an automotive requirement; I need a dash bulb to light when the vehicle is started, then extinguish after about five seconds.

Obviously a 555 timer springs to mind but the circuits I have seen so far assume a mechanical reset button.

Am I missing the obvious?

Regards,

Simon
 

mcasale

Joined Jul 18, 2011
210
Nothing is EVER easy .... and don't call me Shirley.

Automotive stuff is not permitted in this forum.

Run away ...... run away ......
 

wayneh

Joined Sep 9, 2010
17,496
I'd consider adding an RC on the gate of fet to give a soft fade out once the timer has turned it off. Much cooler than just going dark.
 

Thread Starter

Thorfinn

Joined May 23, 2012
3
OOOPS...I prob'ly should have read the posting requirements and rules more carefully - assumed they would be standard boilerpate.

Apologies all. I admit that although I can swing a mean soldering iron, the niceties of circuit design are not my strength...

Regards

Simon
 

MrChips

Joined Oct 2, 2009
30,714
Soft fade...ooh, we're getting fancy.
Ok then, use an 8-pin MCU and PWM the output to the HEXFET.
No external RC required.

If you're willing we can make this an AAC community project and someone can send you the code or even a programmed MCU. That's all you need, an MCU and a MOSFET.

In fact we know someone here who would even make a PCB for you.
 

Thread Starter

Thorfinn

Joined May 23, 2012
3
I'm perfectly willing to lend my personal problem to the world (well, the AAC community) if it's of interest! Be my guest, everyone!

Meantime, many thanks for all suggestions so far. I LOVE the "soft-fade" suggestion....:D

Simon
 

bertus

Joined Apr 5, 2008
22,270
Hello,

I am closing this thread as it violates AAC policy and/or safety issues.

Quote:
6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:

  • Any kind of over-unity devices and systems
  • Automotive modifications
  • Devices designed to electrocute or shock another person
  • LEDs to mains
  • Phone jammers
  • Rail guns and high-energy projectile devices
  • Transformer-less power supplies
This comes from our Tos:
Terms of Service
There will be enough sites where automotive questions can be discussed :
Member selected automotive forums

Bertus
 
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