RogerH Posted July 3, 2017 Author Report Share Posted July 3, 2017 Hi Bill, the TR6 ash tray lends itself to be used for greater things. On the 4/4A it gets you full face so needs to be done sympathetically. Roger Quote Link to post Share on other sites
BrianC Posted July 3, 2017 Report Share Posted July 3, 2017 I was intending to replace the ashtray in Lynda's TR4A with a clock. Smiths positive earth clock (rectangular, requires 2" x 1_5/8" hole size). It's currently on my list of NLR items for sale. If anyone is interested I can bring it to the IWE, but note that it is positive earth so will only be suitable for TR4 and early TR4As which haven't been re-polarised. Quote Link to post Share on other sites
Steves_TR6 Posted July 3, 2017 Report Share Posted July 3, 2017 Hi Roger Hope you are less lumpy now? What method are you using to dim the leds? Ive fitted leds for dash instrument illumination, theyre great but need dimming for night time use. Steve Quote Link to post Share on other sites
RogerH Posted July 4, 2017 Author Report Share Posted July 4, 2017 Hi Steve, LED's need a certain voltage to work unlike a filament bulb that tolerates a little over and a lot under its correct voltage. A LED will not work with too low a voltage and will pop with too high. The difference in too low and too high is quite small. When you set up a LED to work you normally require a resistor to drop the supply volts to the correct value but also allow a certain current flow. It is the current flow that varies the brightness. - somewhere between 0.010 and 0.020 amps. Not a lot. there are a few ways of dimming leds but the typical way is to have a little circuit that turns the LED ON for for mSecs and then OFF for a few mSecs By varying the lengths of the ON's and OFF's you vary the brightness. I think Tony Thompson produce a circuit in the magazine to do this. Or you could google LED dimmer. However if you want them bright or not so bright (two positions) you could use a small SPDT relay that allows the supply volts to the LED (and its series resistor) in the off (day time) position and then add an extra resistor to the LED (and its series resistor) in the ON (night) position. The rheostat switch position could be used to take a change over switch. If you want a pic I'l send you one. Roger Quote Link to post Share on other sites
Lebro Posted July 4, 2017 Report Share Posted July 4, 2017 Further to Rogers excellent description, you can replace the normal rheostat with a potentiometer, which when wired in series with a fixed resistor (to offset the LED voltage drop) will give full control of brightness from off, to max. I have done this on my '3. A bit hard to read, but the variable resistor is 100 ohms, & the fixed one 75 ohms. Can't find the one I used now, but this would do the trick: http://uk.farnell.com/bourns/3852a-282-101al/pot-rotary-cermet-100r-2w-10/dp/1838960 with a bit of either milling or filing the shaft can be modified to take the TR knob + holding spring, & it fits where the on-off switch used to. Bob. Quote Link to post Share on other sites
RogerH Posted July 4, 2017 Author Report Share Posted July 4, 2017 Hi Bob, I thought about a pot but most people get very fretful abut such a simple method. is your diagram for POS earth. If using neg earth the series resistors should be on the 12V side of the pot. Is this right? Roger Quote Link to post Share on other sites
Lebro Posted July 4, 2017 Report Share Posted July 4, 2017 Hi Bob, I thought about a pot but most people get very fretful abut such a simple method. is your diagram for POS earth. If using neg earth the series resistors should be on the 12V side of the pot. Is this right? Roger No & No ! This is for -ve earth, to change to +ve earth the led's need to be turned around the other way, all else remains the same. Bob. Quote Link to post Share on other sites
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