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The G3X and GPS175 comes on with my master switch. There is no offline/reboot after start-up.
+1 This works well.
+2 This is what I have - a small lithium backup battery that supplies the avionics - charged off of the buss. It's basically a "two-fer" - you get to see the EFIS and essential guages upon engine start AND you have a battery backup to the essential avionics should you loose the alternator enroute,
And why do you need to see the oil pressure right after start up? How often do you lose oil pressure? Maybe that is more common for your buddies than the rest of us. I start with avionics off. If you had oil pressure at last shut down, there is an extremely high probability of having it at start up. Mechanical things do not tend to break when they are not being used.
Hence my low oil pressure annunciator lamp off the oil pressure switch for the hour meter.
Recently, I started my airplane and, as normal, noted the increase in oil pressure as the engine came alive, but before I got to the runway, my oil pressure had dropped to 10 psi! Fortunately, I caught it before run-up and take-off. It took less than 5 minutes, according to the engine data collection. Discovered the braided oil pressure hose had worn an almost imperceptible hole through the braided oil cooler hose. Took a bit to find it, but under high pressure, it dumped a lot of oil. The oil cooler hose is now fire sleeved, thanks to TSFlightlines, and I have a flashing low pressure alert on my G3x.
I agree that the chance is pretty small. But it's also not zero. The engine is the single most expensive component in the airplane. In a lot of cases, it's worth more than the airframe. I'm taking every reasonable precaution to protect it.
68 farads??? That's 68,000,000 microfarads! I imagine that would be about the size of my hanger
That's correct! Couldn't find the mu on the keyboard.68 farads??? That's 68,000,000 microfarads! I imagine that would be about the size of my hanger
Probably 68000 uF
I am in no way advocating that folks ignore oil pressure. It just doesn't seem to me that having a 10 second period after engine start with no indication is real risk. One must also bear in mind risk of brown out damage to expensive electronics. Sure, modern electronics deal with it pretty well, but also a non zero risk IMO.
Glad you caught that, but kind of confirms that missing the 10 seconds after start was not really a problem here. I'll reiteate that I feel it is very important to monitor oil pressure, including alarms to grab your attention. I just don't believe a missing 10 second period is really that critical. Just one mans opinion.
Those VT heater elements don't take kindly to the thermal stress that the low-to-high voltage transition causes.I agree. I guess I misunderstood what you were saying re: "Why do you need to monitor oil pressure right after startup?" in the post I was responding to.
I am sure things have changed much in the last 40 years, but I grew up in telecomm in the 80’s and brown out damage, while not common, was absolutely a threat to then modern electronics.Help end this madness -- "brownouts" don't damage, or wear out "expensive electronics", unless we're talking about your Dad's McIntosh MC30 or Fisher 500C
Overvoltage is bad -- think about your own blood pressure. High voltage, Surges, etc. will cause electrical aneurysms -- not good.
Switch mode power supplies (universally used in all electronics these days) can indeed be temperamental or damaged when run at lower than specified voltages, most will have a some protection to guard against this by shutting down but it’s no guarantee. Input current increases as voltage drops, thereby stressing components in the power supply. Boot-up problems are also typical when voltage sags.Help end this madness -- "brownouts" don't damage, or wear out "expensive electronics", unless we're talking about your Dad's McIntosh MC30 or Fisher 500C
Overvoltage is bad -- think about your own blood pressure. High voltage, Surges, etc. will cause electrical aneurysms -- not good.
I think we need to discuss this further -- your assertion seems to run counter to Ohm's law; Current is directly proportional to Voltage, inversely Proportional to Resistance --- V=IR and the other permutations.
WAYYY over my head here, but it would seem that things can't be as simple as just ohms law when dealing with chip based switching power supplies. You are oscillating things at a very high rate and there must be circuitry involved with that. I know some regulator chips specify very wide input voltage ranges and others do not, so there must be many ways to skin this cat. Why would a chip maker specify a narrow voltage range if it could easilly handle a wider range? Again, in the deep end of the pool knowledge wise here without skills, but seems there is more going on here.
I think you answered your own question; lower voltage means higher currents to produce the same amount of power.
), susceptibility to voltage sag/brown out conditions were related to the devices that used thermionic emissions from a "heater" element (tungsten) to function. The rapid cooling and subsequent heating of the element caused by the brown out would make the element break/fail. Suddenly, no more microwaves were coming out of the cavity (magnetron)... or if you were still running with VT's in your SxS or crossbar CO, they would fail for the same reason (1ESS, 5ESS were 100% solid state as I recall, although there may have been some huts along the way that still used VTs in their frames).
Not without reducing the resistance in the circuit.
Well to keep this simple and aviation related, why do 28v systems use smaller wire sizes and breaker ratings than 14v systems to run the same devices?
Because P=IV or P=V^2/R.
I swear you guys could drift a thread from exhaust bolts to how to prep for a colonoscopy and then on to the use of chocolate to catch hangar mice.
Thanks for the detail. I worked on the solid state stuff. cross bar and 1A2 stuff we replaced and didn't really support, though I remember the old timers teaching me about relays and even drum memory. I once designed a work around using E&M tie lines and needed a bunch of relays to do it. Didn't understand shunting diodes at the time and the service went down in a hospital (contacts melted and seized); All sorts of trouble from that learning experience. Remember, I am a sales guy that is self taught in all things technical. Much of that learning was via experimentation and mistakes.Ohm's law describes the relationship of Voltage (Pressure), Current (Flow), Resistance (Resistance), and Power (Watts) -- no matter the complexity of the circuit. It's a law.
The device isn't oscillating (current moving forward and backwards), it's switching On and Off - the width(duration) of the On and Off pulses are is used to derive the output power from the device. The pulsing DC is driven into a transformer or voltage multiplier, capacitors and inductors smooth the output so it appears to be DC without any "ripple".
At the silicon device level, there are limits to how much voltage (pressure) and current (flow) it can handle -- this is determined by the chemical and physical makeup of the device.
In your Telephony days ( me too, 2600Hz and 3700Hz are your friends
Ohm's Law applies to resistors (and circuits that behave like resistors). Many things in the world are basically resistors, like wires, but a switching power supply distinctly does not behave like a resistor. A switching power supply with some device behind it is instead a constant-power load. If you change the input voltage, then the duty cycle of the switcher will change and therefore the current draw will change - but in the opposite direction, in order to maintain the same output voltage.
Yes, a light bulb designed for 28V *must* have higher resistance than one designed for the same amount of power at 14V. But the wiring in the airplane is not the same as the load. The wiring can be thinner in a 28V system because the current is lower for the same power draw.
Switching power supplies are not resistors!
No, they are not Resistors....but they are a circuit, and they have resistance. (and they are not superconductors or anything else when the non-linearity of Ohm's law would apply.)
Might be easier to look in the install manual for CB rating for 14 vs 28 volts.
I was considering doing the same - i.e., a pressure switch with a idiot light on the panel.
2 years old, and will show over 12 volts after it's been sitting for a week or two.
Modern switching power supplies generally regulate current through an inductor to maintain a regulated voltage in an output storage capacitor. The input voltage is switched ON and OFF at higher frequency (12-100 kHz typically) using a solid-state switching device (Transistor, FET or IGBT) to maintain a current level through the inductor to maintain the desired regulated output volage across the output capacitor. Feedback is provided to the switching circuit to either increase or decrease the switching duty-cycle to maintain a constant regulated output voltage across the output capacitor.
Yep..........
Tom, I went through this decision process about a year ago. Maybe this will help…
That was my point, lower voltage = higher current.
