Wiring Advice Please

[ICEMAN]

My radio and I/C have been running off their own batteries, but have occasionally experienced interference throught the intercom/headsets, (buzzing sound which changes pitch with the RPM, which i think comes from my power source for the instrument pod... ).

I have recently purchased a regulator recitifier to install on my plane. To date i have only had a digital instument pod, running directly off my motor (rotax 503, inverted, single ignition).

The wiring diagram for the regulator/rectifier gives two installation options:

1) Motor to regulator then on to the electrical toys eg instruments, strobes etc

2) Motor to regulator, then to battery, then on to the instruments, strobes etc

For both otions it simply indicates to ground the elctrical item.

My questions to the electrical fundies are:

1) Are there any benefits of either installation option (ie with/without a battery in the circuit).

2) Will the regulator/rectifier and/or battery provide some filtering of the interference in the I/C

3) There must be a limit as to how many toys can be installed. I want to power my digital instruments, a nose spot light, a strobe or two and also have a plug or two for additional items at a later stage eg GPS (and also an in line electrical fuel pump in the near future)..... is this too much power drawn through the reg/rec:?: ......

4) What diameter/type of electrical wire is suitable as i can do without an in flight fire caused by overheating of overloaded wires.

5) Is it preferable to earth all the electrics to one single point on the airframe and/or the negative battery terminal (if installed)

Hoping someone has the know-how to give some advice is i would like to get it right the first time around.

FLY SAFE!!!!!!!!!

[Wart]

The battery will act as a large capacitor and assist to filter out interference, so with the battery is better.

The most important thing to note is that you have a common earth for everything.

In order to determine if the regulator will handle all your "toys" you need to determine what current they draw (Amp rating somewhere on the device or in the manual); this would then also be used to determine the diameter of cable to use.

[ICEMAN]

Seems like a battery is the better way to go then :D , it would also ensure that if i had an engine out , i would still have power for the instruments while looking for a parking space


If i place a battery in the systyem and then power (and also ground) the "appliances" from the battery, is its still possible then to overdraw current through the regulator/rec or is the workload then placed onto the battery......

[RudiGreyling]

Good topic,

I also want to ask.

Some guys fit a small 12V 'house hold alarm backup' type battery in the circuit to power the instruments/radio when the engine is off.

1) By fitting it directly as described doesn't these small batteries get overcharged? Do one have to fit a current limiting device for charging these small batteries.

2) What about voltage regulators for the instruments.

Maybe someone in the know, that wire these trikes can give some good feedback, or a schematic diagram.

Thank you in advance.

Kind Regards
Rudi

[ICEMAN]

If a digital instrument system , with rpm gauge, is powered directly off the battery, can it still read the engine rpm?

The system i have is currently powered directly off the motor wiring that comes from the coils, so would assume that it calculates the RPM by "counting" the electrical impulses it recieves?????

Any wiring digram showing the relationship between motor, the regulator/rectifer, the battery AND a digital ins pod (including rpm) all connected would be most welcome

[Morph]

To protect your rectifier from very high currents like short circuits etc you should install a 16 A fuse in between the rectifier and the rest of the circuit.

I have just replaced my battery with a 20 Amp hour battery. Some guys have as low as 12 amp/hour if they don't need an electric start.This will easily drive all the electricals you are talking about, and an electric starter plus your lights, instruments, GPS, Radio Intercom etc. Your rev counter will still be driven straight from the grey wire coming from your coil.

Anyway here is a really nice generic wiring diagram. Although it says it is for for Challengers, but it will be exactly the same as any other plane

http://www.challengers101.com/files/CHI ... iagram.pdf

This one is if you are going digital
http://www.challengers101.com/files/Schem_Digital.jpg

Hope this helps

[ICEMAN]

Thank you Morpheus

[RudiGreyling]

Dankie Morpheus, that helps a lot...

What about even smaller batteries i.e. 6 amp or 3 amp hour 12V just for electronics & radio. Do you need a current limiter and or voltage regulators then in order not to overcharge the battery?

Regards
Rudi

[Morph]

Dankie Morpheus, that helps a lot...

What about even smaller batteries i.e. 6 amp or 3 amp hour 12V just for electronics & radio. Do you need a current limiter and or voltage regulators then in order not to overcharge the battery?

Regards
Rudi

Rudi,

I don't think you will have a problem. The battery will draw as much or as little as it needs to remain charged as long as it is a 12V battery. Try get the sealed type. Check the output voltage of the rectifier with a load, i.e. battery (ideally should be between 15 and 20 ah for this test but just for reference check it with your battery) and a 55W light. With the motor running at 3000 to 5000rpm and the light off the voltage across the battery should be below 14V. With the light on across the battery, the Voltage should be above 13.5V.

BTW a 20 amphour battery is R300, for me worth it if you want to electric start plus have lights, gps, radio, strobes etc.

Here is a detailed rotax doc on testing the output of the rectifier

http://www.gregperkins.co.za/flying/ima ... oke101.pdf

[DarkHelmet]

Speak of lights - where to get some?

[Morph]

Speak of lights - where to get some?

Good question,

I am looking at some nice slimline strobes and a pair of 55W landing lights.

[ACE]

Speak of lights - where to get some?

Good question,

I am looking at some nice slimline strobes and a pair of 55W landing lights.

I have a feeling this came up long ago - best we go & soek !

[Morph]

Yeah I found it here

http://microlighters.co.za/viewtopic.php?t=676

[Wart]

Instead on fitting fuses, there is a product on the market which is a resettable circuit breaker which fits into a standard automotive fuse receptacle. They are obviously a lot more expensive than a fuse but they last a lifetime (and look really smart too!).

Anyone looking for more info, PM me. I will also try and locate the website so that you can have a look at them.

[John Young]

My radio and I/C have been running off their own batteries, but have occasionally experienced interference throught the intercom/headsets, (buzzing sound which changes pitch with the RPM, which i think comes from my power source for the instrument pod... ).

Hi Iceman - you are spot on with your diagnosis.

When I bought my 582, I decided to power the radio (Icom A3) and Buzzcom Intercom from the microlight and get rid of all ignition noise at the same time.

This was effectively achieved by installing a simple RF Choke (total cost is less than R 80). Key components are;

1. Toroid coil (approx 40mm diameter) - cost R 45 (or ask a Ham Radio mate to find you one for free).
2. 2 X 12v voltage regulators - cost R 4 each. Ensure that the radio requires 12v and not 11v)
3. 1 X 16v 2,200 uF (micro farid) capacitor - cost R 2.
4. 2 X small electrical boxes (one to house the toroid and the other to house the voltage regulators) - cost R 4 each.
5. 1 metre of 6 amp twin power cable (red & black - approx 3mm in diameter) - cost R 3

The circuit is simple. Connect to ignition switch (the fuse is normally located between the battery and the ignition switch, meaning that the circuit is already protected). Wind power cord around the toroid about 20 times and fit the capacitor in parrallel after the toroid winding. Split the power cord into two and route each through a voltage regulator. Connect each of the two cords to the power jacks normally provided on the instrument pod for the radio and intercom.



Happy soldering and good comms.

John

PS: My "talking baggage" still glued in the back seat!!