Quinten Posted August 5, 2015 Share Posted August 5, 2015 Background: have installed DRLs (see my thread here) and additional indicators and everything works fine when the engine is switched off. As soon as I start the engine, the DRLs go off (and occasionally on/flicker as if a disco). Wiring is really straightforward, or so I thought (all lights are LEDs). The DRLs also have an indicator function and have this feature called 'switchback', which means that if you apply power to the DRLs, and then power to the indicators, the DRLs temporarily switch off so that the indicators are visible. Once you remove power on the indicators, the DRLs switch back on. This all happens automatically, it's not controlled externally. So I had a brainwave and disconnected the indicators from the above circuit (just the red line, leaving the common ground as it is). And what do you know, the DRLs remain on, even with the engine running. So to my untrained eye, the DRLs get a small enough current on the indicator wire to trick the units to think that the DRLs need to be switched off! But how can I prevent this? Quote Link to comment Share on other sites More sharing options...
CraigHew Posted August 5, 2015 Share Posted August 5, 2015 I'm no auto-electrician but I'd guess at an in-line resistance of some type on the red wire between the indicators and the DRLs. Enough to stop a very small current but not 12v??? 1 Quote Link to comment Share on other sites More sharing options...
Quinten Posted August 5, 2015 Author Share Posted August 5, 2015 Hmm, you mean a small load resistor? Wouldn't that reduce the indicator effectiveness (brightness) of the ones on the DRL unit? Quote Link to comment Share on other sites More sharing options...
CraigHew Posted August 5, 2015 Share Posted August 5, 2015 I'm out of my technical depth really, but I was thinking more of some kind of threshold that the current needs to overcome (ie when the indicator lamp is lit) to complete the switchback operation of the DRL.....? That is if your small trick-current theory is correct.... Quote Link to comment Share on other sites More sharing options...
Quinten Posted August 5, 2015 Author Share Posted August 5, 2015 Well, you may be more 'on the ball' then you give yourself credit for I should have googled before posting (let's just say I wanted to share my brilliant drawing ) as I found this article: http://v-ledsblog.com/2010/10/26/itermittent-blinker-hyper-flash-issues-switchback-quirks/ which amongst other things describes a very similar situation. And it comes down to a small load resistor which raises the threshold for the DRLs to switch off... I'll have to go and experiment a bit with some different load values me thinks... Quote Link to comment Share on other sites More sharing options...
CraigHew Posted August 5, 2015 Share Posted August 5, 2015 Good luck, it shouldn't take much, nor prove too expensive. So long as when the flasher circuit is powered the current can pass to the DRL unit. The outfit selling them should really point this kind of thing out or (for a few pence more) include the correct electrical component in with their product but hey-ho......! Quote Link to comment Share on other sites More sharing options...
Kit Car Electronics Posted August 5, 2015 Share Posted August 5, 2015 Are your current indicators all led or do you also have a normal bulb? Sounds like the red line is floating and needs to be pulled to ground through a resistor. Quote Link to comment Share on other sites More sharing options...
Quinten Posted August 5, 2015 Author Share Posted August 5, 2015 Good luck, it shouldn't take much, nor prove too expensive. So long as when the flasher circuit is powered the current can pass to the DRL unit. The outfit selling them should really point this kind of thing out or (for a few pence more) include the correct electrical component in with their product but hey-ho......! Yes, it would have been ideal, but I guess once it leaves the store, it's no longer their concern :/ Are your current indicators all led or do you also have a normal bulb? Sounds like the red line is floating and needs to be pulled to ground through a resistor. Yes, all my indicators are LED, and my flasher is also specific for LEDs. The only 'normal' bulbs I have are my side/dipped/main beams in the Dominators. So you too would say to add a load resistor? This would go on the red and black, parallel to the indicator on the DRL unit? I know I should have paid more attention in electronics class, but is there any way of calculating what sort of value I should be looking at? 3 Ohm/50W? or 6 Ohm/50W? or...? Quote Link to comment Share on other sites More sharing options...
Kit Car Electronics Posted August 5, 2015 Share Posted August 5, 2015 1K 0.25W between ground and red in parallel with the indicators should do the trick... 1 Quote Link to comment Share on other sites More sharing options...
Quinten Posted August 5, 2015 Author Share Posted August 5, 2015 That sounds like the sort of value I would have in my electronics kit... If you don't mind me asking, but how did you come about these values? From my (very limited) experience I thought the more W, the better it could deal with any heat generated? Or is this a misunderstanding? Quote Link to comment Share on other sites More sharing options...
Kit Car Electronics Posted August 5, 2015 Share Posted August 5, 2015 You don't want to add load (current draw) to the flasher, so 1K gives I=V/R or 0.012A. For 12V that's P=IV = 0.144W, so a 0.25W (or 0.5W) resistor will be fine without overheating. I'd try anything between 1K and 10K for a test, if that doesn't work try a bulb (very low resistance) and if that works then an led ballast resistor should also work if OK for your flasher... Quote Link to comment Share on other sites More sharing options...
Quinten Posted August 5, 2015 Author Share Posted August 5, 2015 Cheers, that's very helpful Have loads of 0.25W resistors (from my Arduino experimental days) in lots of different values so I should just give it a go... a bit of a shame I have to dismantle half the car to do this, but hey ho, hindsight To be continued Quote Link to comment Share on other sites More sharing options...
Quinten Posted August 7, 2015 Author Share Posted August 7, 2015 Just had an epiphany... I can put the resistor anywhere on the red wire (and black of course) right? No need to dismantle the cycle wings again? As long as it is parallel to the indicators it will act as intended? Quote Link to comment Share on other sites More sharing options...
Kit Car Electronics Posted August 7, 2015 Share Posted August 7, 2015 Right 1 Quote Link to comment Share on other sites More sharing options...
CraigHew Posted August 7, 2015 Share Posted August 7, 2015 If you hurry up you can have it sorted by 10pm.... 1 Quote Link to comment Share on other sites More sharing options...
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