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RC delay on circuit

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Bagnell

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Using bits &pieces i have fitted a coolant level alarm to my MGF. It is very simple 12v+ ign operated supply -- LED sw -- Buzzer -- Reed sw operated by magnetic float -- earth. The systenwell but is too sensitive , bumps & fast cornering causing unwanted buzzing ! Will a capacitor & resistor in series giving a 15 sec delay solve the problem ,if so what values should they have &where should they be fitted . Any help much appreciated .
 
I'm assuming that your MG has a coolant resevoir and your float is inside of it. And that there is no way to mechanically dampen the float's movements due to vehicle bump and sway.

Is that correct?

If so, then the RC time constant delayed alarm circuit you're considering is a good start on the concept, but ill-applied in this case (as an alarm delay device).

A workable, although more complicated, solution would be a 555 RC timed voltage comparator circuit.

Do you need me to go further with this concept?
 
Hi Cowboybob - Thanks for your reply - you're right there is no way to dampen the swirl of the liquid - I am using the header tank as fitted to the later MGTF's as by then MG/Rover had got round to fitting a level alarm - as I understand it the "delay on" was built into the engine ECU - an option not available to me.
I looked up 555 Rcs on the net - and Oh dear they are beyond me - my official learning of auto-electrics ended in the early sixties and never continued. to fit something like a 555 circuit I would have to be presented with an exact list of required pieces and a wiring diagram for idiots - too much to ask for, I feel! I would add that the MGF is not the easiest car to work on - bring back the Morris Minor I say!
 
Had an MGB GT back in the early 70's (after a Triumph GT6 and a 69' 427 Vette before that). The MG came with an odd color that I dubbed "baby-****" brown. Had AC but I discovered that the Brits knew nothing about the AC required in South Carolina...

Don't get me wrong, I'm English back to the Anglo Saxons.

Anyway, I can provide a schematic and parts list, if you like.

In the meantime I'll ponder the issue for a bit and maybe I (or someone else on the forum) can come up with a simpler solution.
 
Hey guys. Something that might work is a door prop alarm. https://www.electro-tech-online.com/custompdfs/2012/12/DPA_Series_500-15700.pdf I did see a search that on ebay this was available for $20.

The times are all wacky for relay chatter though. I did not look at the datasheet thoroughly, but it looks like if you can live with 30 seconds and autoreset and the cost, your in. I'd still add, at a minimum a 18 V Transorb or equivalent and a reverse polarity protection diode.

It's a fairly simple job for a small microprocessor and a fair amount of work. The PICAXE might be simple enough. It's programmable in BASIC. The very first job is to build an Automotive quality logic power supply.
 
What is the current required by the buzzer?
 
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