What is the max input voltage for a TTL?

[piratepaul]

In fact ...( thinking continues) I could run the whole thing on separate batteries, except the switching side of the relays...so as long as the relays don't trip ( I am sure I can stop them ) it will definitely not trip the 555 when I turn the engine over.

[piratepaul]

The problem with the RC circuit there Richard is the board is always on, only the ignition switch changes. May be something similar could be wired to the ignition but at present the ignition is not 5v regulated. I don't want to switch the whole thing on and off too often... Induction, switch bounce, and other problems are possible.

[piratepaul]

I take the point about regulation though, if it blows up I will start again, next time with more relays and a separate battery power supply, I only need a relay to ignition possibly ( probably) 2 relays.

[piratepaul]

Well the soldering iron has burned out, I've sent off for a new one ( eBay) so will know if it works when the new iron arrives.

[piratepaul]

Well the new soldering iron arrived today, back to the grind stone in the morn.

[piratepaul]

Well it worked on the bench.

I have a NAND gate, one input goes to ignition via a pot, the other input is fed via a transistor which is triggered via a relay, the board is perminantly on.
When the ignition is off, ignition input is 0 and relay input is 1, when I switch the ignition, the situation reverses, however there is a switching time for the relay so both inputs are 1 for a split second, NAND output is 0 for a split second, the 0 output triggers the 555.
Problem ... The relay takes time to switch off, so the LED comes on when I switch the ignition off... Bolox, bolox, bolox.

I think I can sort out some logic system to solve this, in fact I know I can....just what....tea break.

[piratepaul]

Well I just wired the power 5v power supply to the on/off switch and it works, so now its not permanently on.

Bought a 12v Chinese soldering iron and the handle gets so hot I need an oven glove. Beware cheap eBay soldering irons.

[piratepaul]

Well I just tried it on the car and it works perfect, I now have the engine management light wired to the oil pressure switch, and an airbag light separate from the air bag, I am going to do another 555 for the power steering light.
The reason for the party lights was a slow turbo causing 1 fault code and the engine management light to come on.
So I tried wiring the engine light to a different circuit. The ECU recognised a fault and light the dash board like an Xmas tree.
I still have a fault with the odometbutand clock ( which flashes on and off ) but it does not count for the MOT so I have put sticky tape over it, perhaps I will try to sort it some day when I have time.

I thought I would put this on here just in case anyone else had similar problems. If you have don't desolder any thing the ECU will trigger a take it to the dealer who has the expensive to hire software fault.

Get a new circuit board from the scrap yard for the new LEDs of the same colour, and put sticky tape over the offending ones on the board, so the ECU does not trigger. Hind sight.

[piratepaul]

Hind sight... Something just struck me.

When the ignition is off , 1 NAND input is 1 and the other is 0, the input which is 1 is switched by a relay, the input which is 0 is switched by the ignition, so ... When the ignition is on the delay is on the 0 input so both inputs are 0 for a few ms... So. why does the 555 trigger when I switch off?

[piratepaul]

I wouldn't think switch bounce on switch off but...