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If the transistor gets shorted on though, disconnecting the base won't do anything.

BobM3 - thank you! They have one rated at 6 amps that should work well if epoxied to the transistor and/or heat sink. I will try to find a distributor. xnuke - thanks! That's certainly another option to look into.

Thanks. Ideally if a thermal switch is used, it should be PCB mount (like the to-220 one) I think the polyswitch won't work; I haven't seen one that can handle both the voltage and the current (1-2A@90 up to 240Vac)

I've got an AC circuit that draws about 2A. What I need to do is cut the power to the device should a transistors heat sink overheat (defined as >100C). Preferably until the user unplugs the unit, or at least until it cools down some amount (20C?). It should be resettable, not permanent...

Excellent, thank you! I guess I must have been looking at sheet metal screws or something.

I'm not very familiar with thread forming screws (not to be confused with thread cutting screws) How do you find the appropriate drill size for these? I want to attach two thick aluminum plates together, quickly, without having to tap holes. They seem like the best method, but these "odd"...

Okay, buck boost is bad....... I don't want it blowing up if the load went open circuit. How do I use two strings of LED's at half the voltage (~50V) with one buck converter? Suggestions?

Because according to another app note, you can only use the buck converter if your Vin > 2*Vout. Obviously in my case Vin~Vout, so the buck-boost converter has to be used.

Well the HV9910 will let me get by with about 10 parts. I have a question about ESR though... The ap note wants a 12uF low ESR (tantalum or ceramic) cap on the output. Since my output is >130V, that's a costly proposition. They don't make them, so I'd have to build it out of about $50 worth...

Wow, the actual design of a switching power supply is a bit over my head, but they have a really good app note that walks you through it. Thanks!! (I'll have to search to see if there are similar premade solutions... I'd like to get this up and running soon)

Well if you wanted to get concise, yes! ;) Can you suggest a switching supply with current control off the top of your head? The only ones I knew existed were straight forward fixed voltage..

Sorry, I always tend to muck descriptions up.... It's a diode array that will be powered by mains (120V) voltage. Problem is there is a wide range of voltage tolerance on these devices... Nearly 100%. So these devices will need "somewhere" between 76V-120VDC..... But 0.7A is their maximum...

Here's the problem.... I have a load that varies from 76 to 120VDC, but always needs a constant 0.7A. I figure "okay, no problem, just need to rig up a constant current source for 120Vac use".... In the interests of keeping costs and parts counts low, I decided an NPN current source might be the...

Is there a way to calculate the danger like they do with lasers? I have 18 watts worth of LED's in a reflector. I know it is extremely bright, and looking at it directly for a split second will cause "floating images" in my vision for a few minutes. So I know it's not good to look at, but...

It's hard on the engine in that you can burn up a valve if it hasn't been "calibrated". I'm assuming a race vehicle which does not have a catalyst, has a mechanical throttle, and the installer doesn't want to "calibrate" anything (or is inexperienced). The fuel cut seems to be the best of...

After some googling, I found a sentence that sums up what I understood: "FACT: Timing controls can only reduce 15% of the engine horsepower and are very hard on your engine." That's exactly what I thought, you couldn't get enough control on the engine with just a timing retard. HLC, thanks...

LordMalak - Well at least I don't have to change points! hahaha! So without sophisticated brake actuators, or extra parts (i.e. electronic throttle) is the timing retard the best way? How much can you safely retard the timing at WOT? What are the dangers of doing so? (Burnt valves...

I've heard cutting the spark is bad on the engine/cat/muffler... especially if it backfires when the raw fuel hits the exhaust. But I don't think cutting fuel on a WOT run is a good idea either.

Okay, wheel sensor detects rear wheels are slipping on acceleration. (You floored it from a stop in slick conditions) On the newer engines with electronic throttles, they can just close the throttle a little bit... but if you have a mechanical throttle, how do you reduce engine torque enough...

If I recall correctly, longer intake runners use lower order harmonics to create the "forced induction" effect. Because there are less reflections, the pulses are stronger, and you get a higher VE at that RPM the runner is tuned at. For a first order harmonic, the length of the runner is...