Lebro Posted March 27, 2021 Report Share Posted March 27, 2021 "apart from the initial pulse there are no looses to dim the bulb" How so ? the relay coil must have some resistance. you cheated ! Bob. Quote Link to post Share on other sites
ianc Posted March 27, 2021 Report Share Posted March 27, 2021 Use of overdrive in competition: the Works' TR4 Rally cars (3/4/5/6VC) were equipped with and used overdrive with engines producing about 135-140 BHP. The Works' big Healeys also used overdrive - I don't know on which gears. Their 3 litre engines were producing about 210 BHP in 1963. In his very potent and successful "Beastie"(BST82B), Tony Sheach uses a 28% overdrive on all 4 gears with a 4.875 rear axle. I calculate that this gives him about 20 mph/1000 rpm in overdrive top. His engine produces 170-200 BHP, depending on how he sets it up. Ian Cornish. Quote Link to post Share on other sites
ntc Posted March 27, 2021 Report Share Posted March 27, 2021 homologation ? Quote Link to post Share on other sites
RogerH Posted March 27, 2021 Author Report Share Posted March 27, 2021 1 hour ago, Lebro said: "apart from the initial pulse there are no looses to dim the bulb" How so ? the relay coil must have some resistance. you cheated ! Bob. The DC resistance on a length of 18SWG copper wire is less than half of bu99er all. I didn't cheat, I simply massaged the truth a touch. You must admit it is a neat circuit. It works very well. Roger Quote Link to post Share on other sites
Ian Vincent Posted March 27, 2021 Report Share Posted March 27, 2021 1 hour ago, Lebro said: "apart from the initial pulse there are no looses to dim the bulb" How so ? the relay coil must have some resistance. you cheated ! Bob. +1 Quote Link to post Share on other sites
RogerH Posted March 27, 2021 Author Report Share Posted March 27, 2021 10 minutes ago, Ian Vincent said: +1 By the time the filament has come up to full glow the resistance effect will have come and gone. There is no effect on the bulb glow intensity. Roger Quote Link to post Share on other sites
Ian Vincent Posted March 27, 2021 Report Share Posted March 27, 2021 I still think that is effectively the same thing as a relay. Rgds Ian Quote Link to post Share on other sites
RogerH Posted March 27, 2021 Author Report Share Posted March 27, 2021 (edited) Hi Ian, you were very close. However a normal smallish relay has quite a high resistance so would have a significant effect on the glow. Also the bulb is drawing apprx 2amp - the relay coil would not like that - something has to give and it would be the intensity. Roger Edited March 27, 2021 by RogerH Quote Link to post Share on other sites
tthomson Posted April 3, 2021 Report Share Posted April 3, 2021 Hi Roger, In your diagram, unless you have a positive earth car, the LED is the wrong way around. TT Quote Link to post Share on other sites
Lebro Posted April 3, 2021 Report Share Posted April 3, 2021 Agreed Bob. Quote Link to post Share on other sites
RogerH Posted April 3, 2021 Author Report Share Posted April 3, 2021 23 minutes ago, tthomson said: Hi Roger, In your diagram, unless you have a positive earth car, the LED is the wrong way around. TT Hi Tony, it will work on positive earth with a few changes. The LED (or in this case the DEL) was put in hastily in the drawing.. But it really does work n practice. Roger Quote Link to post Share on other sites
tthomson Posted April 3, 2021 Report Share Posted April 3, 2021 Hi Roger, I wasn't being negative, I think it is an elegant solution. I thought perhaps you were making use of an N-Channel Enhancement mode MOSFET to sense a voltage change at the lamp, but that would have required a fairly complicated means of determining the current through the wire - causing serious brain ache. Instead the reed relay is sensing the current change to do exactly what is needed. Clever! I love the simplicity. TT Quote Link to post Share on other sites
RogerH Posted April 3, 2021 Author Report Share Posted April 3, 2021 Hi Tony, I didn;t think for a minute that you were being negative. Most of the replies above I had considered but they all had big(ish) drawbacks. The reed relay had the fewest issues. Roger Quote Link to post Share on other sites
tthomson Posted April 3, 2021 Report Share Posted April 3, 2021 It is possibe to get changeover reed relays so you could use a twin colour LED to show both operating and failed lamps, but that gets more complicated again. TT Quote Link to post Share on other sites
RogerH Posted April 3, 2021 Author Report Share Posted April 3, 2021 8 minutes ago, tthomson said: It is possibe to get changeover reed relays so you could use a twin colour LED to show both operating and failed lamps, but that gets more complicated again. TT Ha Ha - I would have a dash like a Christmas tree - very bling. Roger Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 10, 2021 Report Share Posted April 10, 2021 Found the passing contact switch you could use Roger From a Route Master Quote Link to post Share on other sites
RogerH Posted April 10, 2021 Author Report Share Posted April 10, 2021 Just the job Roger Quote Link to post Share on other sites
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