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mrinalmani - sorry, forgot to answer your other question. The strobe fails immediately upon power on ... in the hangar ... at airspeed zero! Static discharge isn't the issue... As I've said, I believe the issue is that I'm getting a reverse voltage spike after driving the approx. 14 foot long...
To esp1 - THANKS! Here's the schematic. I'm using a different Cree LED pn (a 3V device instead of the original 9V device), and an L78L05 instead of the LM7805 regulator, but the rest of the circuit is unchanged. It's pretty simple... the PIC controller strobes the 2N2222, which either pulls...
Hi esp1 - yes, thanks, I actually chose the L78L05 because the current drive of an LM7805 was far more than the PIC controller required. The L78L05 is only used to drive the PIC12F1501 controller, which never gets close to 100MA of current requirement. I know this not just because of the spec...
Hi team - I've been over in the electronic elementary questions forum trying to get some ideas on a problem I'm having where a homebrewed strobing 5A LED power supply keeps frying.
This is an LED strobe system I designed for use in my experimental aircraft. It's working fine in one...
Finally had a chance to try a modification again today... I put IN4005 protection diodes across the LED string (on the power boards, between the LM338 and the IRF510, cathode to the LM338 side), and I also put a IN918 protection diode across the L78L05 regulator. Once again, it tested fine on...
(sorry if this gets posted twice!)
Supply voltage: 12 - 14V (13.8V nominal)
LED (XMLBWT-00-0000-000LT60E3) voltages:
Vr: 5V
Vf: 2.9 - 3.5V (3.1V @ 1.5A)
There are two LED assemblies, 8 LEDs per assembly
Each LED assembly is driven by it's own LM338/IRF510 "Power" card. Both power cards are...
Wow, once again, SunnySkyguy rules!
Just background - I'm driving the LEDs at 5 amps - two separate LM338/IRF510 power boards each driving 5A, driven by a common PIC controller... one LED string for each wing (8 LEDs/string in parallel).
Regarding SMPS - the Murata/Oki 78SR series looks really...
Wow, thanks to SunnySkyguy! Great response.
I guess if the design is a little "mickey mouse-ish" due to lack of consideration of ESR, that's my bad - the design is mine. And yes, believe it or not, I did spend some time looking at alternative mosfets on Digikey, but because I'm pretty sure...
Thanks, esp1! Yes, it's a typo... should have said LM7805, but in actuality I'm using the small, 100ma version (L78L05). Regarding putting a diode in parallel, I'll try it - but thinking this through I'm not sure I understand the theory. The diode would conduct if the output rises to 13.8 +...
Hi team!
I'm struggling to figure out why I keep frying a 5V regulator and a PIC controller on a very simple LED strobe system!
I designed two simple cards, one with a PIC controller, and the other with a linear current limiter (using an LM338) and a mosfet (IRF510A). The PIC just creates a...
Analog Ground wins with what's got to be the right answer - followed closely by Audioguru! To both of you - thanks very much, I was reading the spec wrong... Audioguru said it best "The threshold voltage Vgs(th) of a Mosfet is when it is almost turned OFF not when it is properly turned on."
I...
The measurements I supplied in the original post were taken directly off the leads of the mosfet:
Vds = 3.2V
Vgs = 4.94V
Vdg = 1.72V
But, boy are you right... it just doesn't seem like the mosfet gate voltage is high enough even though I'm exceeding the max spec'd Vgs(th) threshold voltage...
Thanks! Here you go:
http://www.allcomponents.ru/fairchild/irf150153.htm
- - - Updated - - -
Vin is about 14V (the electrical system is essentially the same as a car - alternator, regulator, etc.). I use a 5V regulator to provide power to the PIC controller. And... You are Correct... the...
Thanks, alexan_e - can you explain what you mean by "high side switch"? Do you mean having the switch (in this case the mosfet) between the load and the rail?
Thanks again - very much appreciated!
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