I recently picked up a 6.5" TFT on ebay for a modest amount. The screen came minus means of connecting it in the car. I have checked the specs and it states a supply voltage of 11-14v. Would it be safe enough for me to assume that I can run this straight off the switched 12v feed in the car? Sorry in advance if its a bit more than obvious what the answer is. Thanks MJD
Without looking inside to see if any regulation is already fitted, I'd use a low-dropout regulator like one from the MIC29xxx range set to around 11.5V. A car supply will be very noisy so the filtration of the datasheet example circuits will help.
I understand the concept, but how do I go about installing the regulator? (What does it look like in the flesh?) As you can see I have no idea when it comes to these things.
also remember that when you use the starter the battery voltage can drop to almost nothing, so the TFT would switch off momentarily. might even cause damage. you may want to look into a capacitor or something?
Like a power transistor with 5 pins, the typical circuit is like this but you can use a cheap preset potentiometer to set the output voltage, or calculate the fixed resistor needed instead of (R1+VR1). I'd also add a 25V 1000uF capacitor to the front end in parallel with C1. Do you know what current the screen needs?
I did mine a few weeks ago and used a LD1084v12. Any advantages with the MIC29xxx? Here's mine sans heatsink (just the little perf board) The other harnesses are because I've ditched my headunit and am powering it off of that. My lilliput had a crappy regulator so I just cut the wire off of that, but you could make one easy enough if you don't have a car adapter. The Lilliputs and Xenarcs are supposed to be ok with that (not be damaged), but my lilliput will get wonky if it's on when I crank it. Flipping it on and off fixes it. At some point, I'm meaning to address it.
LD1084 - "Dropout is guaranteed at a maximum of 1.5V at the maximum output current, decreasing at lower loads." MIC29xxx - "these regulators feature 300mV to 370mV (full load) dropout voltages" "That's not a knife...That's a knife". But they're expensive compared to the 1084 Either forget the 1000uF cap or add 2 x 4700uF in parallel to be safe on the ripple current rating. They're about 60p each, not expensive.
Okay, again the concept seems straight forward, but I am really looking for a walkthrough as to how I do this....imagine a 3 yr old child.......now half it's IQ......and you should now be in a position to point me in the right direction Ideally I need a list of parts required and how to connect it all up. I appreciate this is n00b-esque, but we all have to start somewhere.
You might want to go with the LDO108412v then. It's simpler to set-up. Only three pins (INPUT,OUTPUT,GROUND). Then you just need two 10uf capacitors. If you look at figure 2 in the link, application circuits, that's pretty much it. Just make sure you install the caps the right way if they are polarized and keep in mind that the ordering of the pins in the schematic is not the same as the physical package. (Ground isn't the middle pin for instance). Then you run battery +V to Input, Ground to Ground, and Output is the regulated 12v for the LCD. Also make sure you have an appropriate sized fuse on the lead from the battery.
Thats a bit more suited to my ltd ability. Just one question - my HU has a prewired tap in the switched feed, as such would I still need to fuse it?
If the wire is fused correctly, these have overload protection so you probably could do without, the original fuse will protect the wire but not you're 3amp lcd. I normally put another fuse that's just big enough for the device to protect it. In your case, you might want to put a 3amp before it. What are you wiring it to? When you say the switched feed, you mean the radio power or amp turnon?
Thats what I'm using, but no radio anymore. If you still have your HU, you might blow a fuse if you're pulling too much current through the circuit.
