08-21-2011, 06:59 PM
I have an Escort Passport SRX installed radar/laser system in <acronym title='model year'>MY</acronym> coupe that was installed by the previous owner. The ‘concealed display’ is a dual-junction LED (red/green) that provides the status of the detector and was mounted in the top of the instrument cluster bezel. I wasn’t entirely satisfied with its placement or functionality, so I’ve decided to come up with something else…
In thinking of where I would like to receive a radar/laser warning, the first location that came to mind was the instrument cluster. But where? In all except Japanese models, the indicator on the left side of the cluster opposite the high beam indicator is not used. Perfect! This location has no light bulb installed, and is blanked by an opaque black plastic piece. This should work nicely.
Fabrication began by creating a new light filter to replace the blank. The prototype was created from clear (I couldn’t readily find a satin finish) smoke colored plastic which I ‘satinized’ using a very fine sandpaper. Ok, actually is was <acronym title='model year'>MY</acronym> wife’s nail polishing block, but please don’t tell! <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" /> I then used tail light repair tape to apply a red filter to the backside. Like the high beam indicator, it appears black from the front, but when light is shone through, it is colored. The filter is done.
On to the light source… I wanted to find something that would have the same luminous intensity as the high beam indicator, which is a 12V, 1.2W bulb. Instead of doing a bunch of math – lumens, candelas, and steradians, oh <acronym title='model year'>MY</acronym>! – I chose to wing this one. The first thought I had was to use a high intensity white LED. This would require about 3V and 25mA for nominal operation and provide a 7cd of luminous intensity. In testing I found the Passport can only output 8-10mA of current, and the LED voltage is only about 2V. This was not going to work.
Porsche knows best, that’s what I told myself when I abandoned the LED idea and decided to go the route of using an OE 1.2W incandescent bulb. This poses some immediate challenges. An incandescent bulb draws A LOT more current than a LED. There’s no way the Passport can hack it, I tried. And, how do I get power to the darn thing?
The first of these problems is nearly solved. I took it upon myself to design an amplified switch to drive 12V loads using input provided by the Passport’s concealed display output. I came up with an optoisolator which drives a transistor amplifier configured to operate as a switch. After staying up until 5am, I have the circuit schematic, the bill of materials, and the circuit board design ready to go. All I need to do is order the materials and have the PCB manufactured. <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" /> In its most recent design iteration, the unit will take two LED level inputs and drive their respective nominal 12V loads at up to 500mA, but I only need 100mA for the 1.2W bulb. It will not interfere with operation of the Passport, as it has been designed to operate just as the original concealed display.
So, after reading all of this… I’m curious if anyone else has a Passport installed detector system and if any of you would be interested in a prototype? This will work for converting most any LED to a 12V 500mA switch, too! The cost of components is cheap, less than $20 a unit, and I’ve got to pay the fixed costs anyways… So let me know what you think!
Now, on to figuring out how to get power to that bulb… should be easy, really, use the 12V supply that is already present, then just have to provide a return path through the switch via connector B, pin 11. <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />
In thinking of where I would like to receive a radar/laser warning, the first location that came to mind was the instrument cluster. But where? In all except Japanese models, the indicator on the left side of the cluster opposite the high beam indicator is not used. Perfect! This location has no light bulb installed, and is blanked by an opaque black plastic piece. This should work nicely.
Fabrication began by creating a new light filter to replace the blank. The prototype was created from clear (I couldn’t readily find a satin finish) smoke colored plastic which I ‘satinized’ using a very fine sandpaper. Ok, actually is was <acronym title='model year'>MY</acronym> wife’s nail polishing block, but please don’t tell! <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" /> I then used tail light repair tape to apply a red filter to the backside. Like the high beam indicator, it appears black from the front, but when light is shone through, it is colored. The filter is done.
On to the light source… I wanted to find something that would have the same luminous intensity as the high beam indicator, which is a 12V, 1.2W bulb. Instead of doing a bunch of math – lumens, candelas, and steradians, oh <acronym title='model year'>MY</acronym>! – I chose to wing this one. The first thought I had was to use a high intensity white LED. This would require about 3V and 25mA for nominal operation and provide a 7cd of luminous intensity. In testing I found the Passport can only output 8-10mA of current, and the LED voltage is only about 2V. This was not going to work.
Porsche knows best, that’s what I told myself when I abandoned the LED idea and decided to go the route of using an OE 1.2W incandescent bulb. This poses some immediate challenges. An incandescent bulb draws A LOT more current than a LED. There’s no way the Passport can hack it, I tried. And, how do I get power to the darn thing?
The first of these problems is nearly solved. I took it upon myself to design an amplified switch to drive 12V loads using input provided by the Passport’s concealed display output. I came up with an optoisolator which drives a transistor amplifier configured to operate as a switch. After staying up until 5am, I have the circuit schematic, the bill of materials, and the circuit board design ready to go. All I need to do is order the materials and have the PCB manufactured. <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" /> In its most recent design iteration, the unit will take two LED level inputs and drive their respective nominal 12V loads at up to 500mA, but I only need 100mA for the 1.2W bulb. It will not interfere with operation of the Passport, as it has been designed to operate just as the original concealed display.
So, after reading all of this… I’m curious if anyone else has a Passport installed detector system and if any of you would be interested in a prototype? This will work for converting most any LED to a 12V 500mA switch, too! The cost of components is cheap, less than $20 a unit, and I’ve got to pay the fixed costs anyways… So let me know what you think!
Now, on to figuring out how to get power to that bulb… should be easy, really, use the 12V supply that is already present, then just have to provide a return path through the switch via connector B, pin 11. <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />