Voltage spikes

[Old Koreelah]

I recently returned my strobe unit to Pennsylvania for repair- for the second time. Diagnosis: voltage spike or stray voltage. This time they are installing a heavy-duty chip. I have a Jabiru engine and standard Jab regulator. Can anyone recommend a reliable voltage filter that would protect my iPhone and iPad?

 

 

[robinsm]

I had a problem with spikes in my Xcom radio, installed a seperate battery circuit, which could be taken in and out of the main circuit by a dash switch as a filter Works a treat. I found the spikes were occurring at startup. I start the aircraft and then switched the radio on. I run a 582 and use a key west regulator.

 

 

[Old Koreelah]

I had a problem with spikes in my Xcom radio, installed a seperate battery circuit, which could be taken in and out of the main circuit by a dash switch as a filter Works a treat. I found the spikes were occurring at startup. I start the aircraft and then switched the radio on. I run a 582 and use a key west regulator.

Thanks for that, robinsm. I had presumed that my car-style ignition key switch would isolate everything bar the starter while cranking. This would cover the situation of an unexpected restart while idling, when I might forget to switch off radio, etc.

The damage might have followed when I have left strobes swiched on at shutdown. My wiring is pretty simple; on startup everything without its own switch is powered up. this includes two cigarette-lighter outlets which power chargers. Might have to install a separate power feed for those sensitive items.

 

 

[cscotthendry]

One item that causes spikes that most people overlook is the starter solenoid. The solenoid itself draws a fair bit of current and when the start button is released and the solenoid disengages, it creates quite a voltage spike. One solution is to install a hefty snubber diode across the control input of the solenoid. The diode is connected fron the control input to ground with the negative end of the diode (the end with the stripe around it) to the solenoid control input. That way when the solenoid creates the spike, it is shorted to the Ground. This should also be done for any other relays in the system, or alternately, install relays that have a snubber resistor connected internally.

 

Google "snubber diode" to see schematics and better explanations of this effect.

 

 

[Kyle Communications]

For safety sake for all of your electronics EVERYTHING in avionics and power supply should be on their own switch or on a group switch. NO equipment should have 12 volts present at its terminal at engine start. Once the engine is running then switch it all on...this way no unwanted spikes from anything...unless of course the alternator or reg stuffs up then not much can help you there

 

I just came across this issue recently when fault finding a fox bat radio installation. The Xcom was occasionally going a bit stupid and not transmitting but would RX fine. It turns out when the master is on the circuit prenets the radio with 12 volts there is no isolation swtich for the radios power supply. When the engine was started occasionally because the radio is a "soft on" in other words the microprocessor sits on the 12 volt input so if the 12 volts is present there the micro wakes up and is waiting for a ON command...when the engine is started the volts collapse down to 10 or sometimes 9 volts and this can screwball the microprocessor occasionally. The easy fix is to put a switch in the positive live to the radio...no more problems.

 

Mark

 

 

[jakej]

Mark,

 

Spot on

 

What surprises me also is that most of the RA aircraft do not have any spike protection on the starter solenoid (only needs a simple 1N 5400 diode), & in the case of Jabbys especially, do not have a battery master solenoid as well:scratching head:

 

 

[Jabiru7252]

Installing a 'heavy duty chip'. Yea, what the hell does that mean? Maybe I have been out of electronics too long.

 

 

[Kyle Communications]

Layman's terms maybe for a higher current output device

 

 

[jakej]

Probably means an Electrolytic Capacitor which should be on the bus output wire from the regulator, that will clean up the dirty ripple current fromm the alternator & make life better for radio ops - all the Rotax engines have them ,usually but it's probably about penny pinching in some cases:oops:

 

 

[Kyle Communications]

Jake

 

I like the rotax manual it says we recommend a 22,000 uf cap put there but they dont supply it. I have seen quite a few rotax installs without it...it also protects the regulator if you turn off the master before the mags...apparently you can take out the regulator easily if you dont have the cap there

 

 

[Jabiru7252]

I'm just a grumpy old man. Being an ex radio/TV techo I find some of the explanations and terms used to describe things to 'non-electronic' people to be quite amusing, and a little condescending at times. A bit like blaming 'a computer glitch' when the bank loses its ATM network. Treat everybody as a dummy. Like when my sister took her car in for a service (just a service) and the bloke tried to flog her a new frammin for $600 because hers was knackered. By the way, it's been FIVE WEEKS since I sent in my rego papers - still nothing. It's just great outside and my plane is stuck on the ground.

 

 

[Kyle Communications]

Sorry to rub it in but I went this morning for a fly to calibrate the new firmware in the compass module of my SP6 used in the MGL series of EFIS...and it was just fantastic...like glass on the way out to Kilcoy but a bit lumpy on the way back...thermals were quite strong this morning.....I got my rego back right on the day before it was due

 

 

[jakej]

JakeI like the rotax manual it says we recommend a 22,000 uf cap put there but they dont supply it. I have seen quite a few rotax installs without it...it also protects the regulator if you turn off the master before the mags...apparently you can take out the regulator easily if you dont have the cap there

Yeah Mark

 

The 'cap' is an item I use on every permanent magnet alternator for the reasons explained earlier, gets rid of the patchwork of ferrites that some people use as some don't understand the 'issues'

 

On another topic - did you have some issues with the radio re transmission unit a couple of weeks or so ago, I tried to use it but the reception back was poor? However I was just west of Gympie at the time but as I don't know the exact location of your system I wasn't sure if I was too far away.

 

 

[Kyle Communications]

Hi Jake

 

Yes the simplex repeater is out at the moment it has failed. It had very poor retransmit level. I installed the module into a IC-A110 and the recovered audio seems to have a lot of baseband noise in it I wasn't that happy with it so have been looking at putting it into a different radio the interfacing to the A110 was a real bugger anyway. I removed the module and put the A110 here at the workshop as my listening radio and pulled the A200 off the bench and have fitted the module to it but I think the simplex module has an issue with it as the squelch line it uses for keying is acting strange I have tried a separate open collector to key the unit record sequence off the radio and it records great then starts button pushing itself. I then used a hard ground via a relay and it was doing the same so I think the module has a problem and there is no schematic for it I can find so I have ordered a couple more modules they are about another week away as they come from the USA. The A200 is ready and waiting for the module I will see how well it performs then but I think I may go eventually to the good old crystal controlled tait T373 I have a brand new one still in the box here just cant be bothered ordering crystals from HyQ but think I will get it under way. So next time you are up this way you hopefully will get a better response.

 

Mark

 

 

[Jabiru7252]

VERY loosley stated; Ferrite beads are used too smooth current fluctuations and capacitors smooth voltage fluctuations, the latter being more hazardous to radios etc. As an apprentice I was often installing car radios and we would use a capacitor across the points to limit the voltage spikes and often wind the radios power lead around a ferrite rod to stop hash (alternator whine) getting into the radio. (through the power lead). Each has its place. It can make interesting reading on those days when the weather is rubbish for flying and you are barred from the pub.

 

 

[jakej]

VERY loosley stated; Ferrite beads are used too smooth current fluctuations and capacitors smooth voltage fluctuations, the latter being more hazardous to radios etc. As an apprentice I was often installing car radios and we would use a capacitor across the points to limit the voltage spikes and often wind the radios power lead around a ferrite rod to stop hash (alternator whine) getting into the radio. (through the power lead). Each has its place. It can make interesting reading on those days when the weather is rubbish for flying and you are barred from the pub.

What I've found is some people are using the ferrites all over the place as they've heard from the grapevine that that is a way to fix their radio/audio issues without understanding the root causes. As a result of the lack of understanding & poor installation methodology there are some very poor radios transmissions out there which is just so unecessary. One of my pet gripes is not seeing mic muffs fitted - as you will know they attenuate the noise better & stop spit & dust ruining them, a mic muff saves money too by prolonging the replacement of the mic.

 

 

[jakej]

Mark

 

Thought the repeater was out - at least I hoped it wasn't my radios. I'll add my thanks to you for setting up the system, keep up the good work

 

 

[Old Koreelah]

Installing a 'heavy duty chip'. Yea, what the hell does that mean? Maybe I have been out of electronics too long.

This is how the factory explained it:

"...looks like the same IC were blown as in 2010. This type problem is usually caused by a voltage problem. Either a voltage spike or stray voltage. I am going to upgrade this unit with a Smart Card. The 12 volt card will only take about 18 volts and the Smart Card will take about 100 volts..."

 

 

[Old Koreelah]

JakeI like the rotax manual it says we recommend a 22,000 uf cap put there but they dont supply it. I have seen quite a few rotax installs without it...it also protects the regulator if you turn off the master before the mags...apparently you can take out the regulator easily if you dont have the cap there

Crikey, it seems the more I read, the more ways I can stuff up my plane! Does this mean that if my shut-down procedure is a bit sloppy, I can cook the regulator?

 

 

[cscotthendry]

This is how the factory explained it:"...looks like the same IC were blown as in 2010. This type problem is usually caused by a voltage problem. Either a voltage spike or stray voltage. I am going to upgrade this unit with a Smart Card. The 12 volt card will only take about 18 volts and the Smart Card will take about 100 volts..."

The voltage spike that kills stuff comes from the starter solenoid and it is a negative spike, not a positive spike. I could go into the physics of it, but it would take me forever to type it on this stupid iPad. In any case, most electronic devices are fairly tolerant to reasonable overvoltage events. What most won't tolerate though is reverse polarity. This is exactly what happens when the solenoid is released, it generates a negative voltage spike back through the system. That is especially damaging to CMOS devices like microcontrollers that are found in most modern radios and transponders.

 

 

[Old Koreelah]

Thanks Scott, Mark and the others, for your responses. I will be installing a main switch downstream of the starter key and will be religious about shutting it off before hitting the starter.

 

 

[Guest Andys@coffs]

If we are stating practicalities Ferrites that we might have access to are good for stopping VHF RF...which in the case of this thread is probably completely unrelated. As for inductors or capacitors.....Generally on ground based things I use both in a Pi Filter format. In an aircraft generally Caps are more weight friendly than an inductor suitable to the task.....

 

For those who aren't sure of what Im talking about

 

gives a reasonable overview. The only thing I object to is that he says words to the effect that he doesn't know what the inductance value will be at the frequency in use......Its simple to work out using formula's and anyone designing a filter will not just generally suck it and seeAndy

 

 

[sain]

I recently returned my strobe unit <snip> Diagnosis: voltage spike or stray voltage. <snip>

This is how the factory explained it:"...looks like the same IC were blown as in 2010. This type problem is usually caused by a voltage problem. Either a voltage spike or stray voltage. I am going to upgrade this unit with a Smart Card. The 12 volt card will only take about 18 volts and the Smart Card will take about 100 volts..."

so umm.. this might be a stupid question, but why the f**** would you need a smart card to drive a strobe? I don't generally like to question repairers, but that really sounds to me like they are talking out of their a****.

 

Okay, I can see using a microcontroller if you've got an all singing, all dancing strobe that will flash in time to some doof-doof music your listening too as your taxing around in your fully sick, hotted up, chrome plated Jodel d9 (or some other more useful application). But even then I don't see how the smart card would help - most of them run at 1.8, 3.3 or 5V. If your going to use one to flash lights, you then need to provide it with power through a regulator and appropriate LC filter. Wouldn't you be better of just fitting a proper regulator and filter to the strobe in the first place?

 

edit: *possible enlightenment dawns* oh - are they talking about some proprietary PCB they stick in with better regulation and filters, that they are calling a "Smart Card"?

 

 

[Old Koreelah]

...Okay, I can see using a microcontroller if you've got an all singing, all dancing strobe that will flash in time to some doof-doof music your listening too as your taxing around in your fully sick, hotted up, chrome plated Jodel d9

Gee Sain, what a great idea. I must add these features to my little plane right away!

 

...edit: *possible enlightenment dawns* oh - are they talking about some proprietary PCB they stick in with better regulation and filters, that they are calling a "Smart Card"?

Sure beats me. I have enough trouble joining two wires together, without trying to understand how these things work.

 

 

[Jabiru7252]

I have loaded a photo that describes the simple circuit used for starting most of our aircraft engines. When you press the starter button, electricity flows from the positive terminal of the battery (using conventional flow not electron flow here) through the starter switch, through the solenoid coil and back to the negative terminal of the battery. This causes the core in the solenoid to pull the big heavy contacts closed allowing the heavy starting current to flow from the positive terminal through the contacts, through the starter motor and back to the negative terminal, via the chassis in my drawing. When you release the starter button, the spring in the solenoid returns the contacts to the open position. If the contacts in the solenoid weld shut (can happen, google it) then your in trouble because, unlike a car, it is pretty hard to pop the bonnet and disconnect the battery, so you watch your enigne cranking over until the battery goes flat or the starter motor burns out. Now, when the starter button is released the magnetic field in the solenoid coil collapses and thus generates a high voltage (opposite to the applied battery voltage) and that voltage spike, which can be a few hundred volts can wreck things. I cannot see why a diode across the coil, wired the right way is not used to 'short out' the back EMF. Anyway, that's my lot, hope I have been of some use.