I just finished building a Hobbico UltraTote field box. The kit came with a "Deluxe Power Panel II". I've charged the battery and tested all of the plug-ins to make sure they work and everything does (starter, fuel pump, glow plug, glow plug recharger). There is also a meter on the front of the power panel that reads "DC Amperes" and has a scale from 0 to 5 with 5 being in the red end of the spectrum. I have yet to see this needle move. Is the purpose of the meter to tell me how much juice is left in my field box battery? If so, then this thing ain't working...

Thanks in advance.

If you connect a glow plug the meter will move, it is there to show current to the plug and with a little use you will be able to determine not only that the plug is good but if the engine is flooded, etc.

I am not familiar with that panel so I do not know what the meter should show with a new plug, your instructions should have this info and should be adjustable.

CheesyD,

It shows the current drawn by the glow plug. This is very useful as you can tell if the plug is drawing current without taking it out of the engine.

John

If it's the same Hobbico Box that I just put together myself (And used today) it is showing you the current draw on the battery from your glow plug. Then you also have a knob which allows you to adjust the current flow to the Plug.

If you look at the meter is has a range of colors on it........ when connected to the Glow plug, turn the dial until you are in the green, then fire the engine up.

when setting the temp for the glow starter ,keep in mind that most glow plugs are rated at 1.5 volts .

there are some that are rated as high as 2 volts be careful not to burn your plugs out by putting more than the rated volts , the knob that is there adjusts the volts that you put in !!!!!!

Highlander

Uh-h, if the meter reads DC AMPS, then it's controlling the amps being fed, not the volts.

Amps are not "fed", they are drawn. Volts are "fed". Current (amps) can be limited, however. Semantics! Start the thing and fly it, man!

In any case, before you attatch it to your plug, turn it down all the way, then attatch it. Turn it up to where you want it. I run it hot, just under the red. Everyone if different there. I like the panel, but don't like the wire running to the plane any more. Used it for longer than I care to remember. They do work well though, and if you need more juice, you can dial it in.

N7OR,
You're right of course. I realized what I'd written as soon as I posted, but didn't bother to edit.
Dennis-

I would like to be there when you feed straight amps into your glow plug DB.

Highlander

Highlander,
Voltage = Current times Resistance. You can't have one without the other. So you cannot feed straight amperage or voltage. In the case of a glow plug its resistance is low. If you feed the plug 1.3 to 1.7 volts you will see a larger current swing. Because of the larger current swing, that is what is monitored on most control panels. Not voltage.
Later,
John

Since we are talking DC, you have V=IR, or more to the point, I=V/R. R is the glow plug resistance, which should be constant (more on that in a moment). V is what you adjust with the knob, it does change the voltage of the output. I (the amperage) is what the needle shows you, it's telling you what the result of turning the knob to a particular setting is. So, you adjust the voltage which gives you a resulting current. Knowing the current produced for a specific voltage is more useful than just knowing what voltage you set the knob to. The same knob position always results in the same voltage. (in theory anyway)

Now, R (the plug) should also be pretty constant. If it changes, it can tell you things. It can tell you that your plug is going bad, or if the engine is flooded or not primed, etc. In general, the knob setting should result in the same needle reading particular plug all the time, if it doesn't, then something is happening that you might want to be aware of.

Personally, I went to a cordless nistarter thingie a while back for convenience, so I don't remember exactly what changes to the amperage mean anymore, other than the obvious readings of "nothing" and "everything".

If you feed the plug 1.3 to 1.7 volts you will see a larger current swing. Because of the larger current swing, that is what is monitored on most control panels. Not voltage.





the current swing that you speak of I assume is the equivalent to current draw which you are correct in seeing as amps , the current fed is volts and most of the standard glow plugs are of the 1.5 volt type , they will however with stand more voltage than rated to a point , before they burn , which was my warning to cheesyD ,nothing more nothing less.

want to try for yourself turn the knob to deliver maximum Voltage to the glow plug and hook it up to your plane ,

Highlander

Highlander,

I would like to be there when you feed straight amps into your glow plug DB.

I'll try this one more time. Having been in electronics since I was 10 and an Electrical Engineer for too damn many years, all I was trying to get you to understand is that these are not unrelated quantities. One relates to the other. You cannot have an electrical flow without having an energy potential ie volts that is then regulated by the resistance of the load. The flow is then measured in amps. You need all three do do work.

Sorry for getting so far off the subject.
John

ahhhhhhhhhh but I have to chime in...... being an EE myself.......

by turning the knob you are changing the impedence to the circuit and thereby changing the amount of current that can flow through the plug. Ohms Law states that I = V/R when increasing the "R" you decrease "I", or current, which is what is shown on the panel meter. You are varying the current flowing through the plug by increasing or decreasing the circuit resistance, or "R". The voltage supplied to your panel is fairly constant at 12 volts (Assuming the battery is fully charged and not heavily loaded).

When you increase the impedence to the circuit you drop more voltage across the potentiometer, which is controlled by the knob, and thereby have less voltage "Felt" at the glow plug.

The voltage in the circuit as a whole is fixed at 12 volts DC. What varies is how much voltage is felt at the plug, and the current flowing through it.

As JNorton stated...... It is all related. Bottom line is that the knob adjusts how hot your plug is.......

Resistance is DC only
Impedance = Resistance + j*Reactance [AC can contain a complex "resistance" called reactance]

Since your plug is DC, there is no reactance, hence impedance is resistance only.

And the real Ohm's Law is J=Sigma*Epsilon, where J is current flux density, sigma is conductivity and epsilon is the electric field. J and Epsilon are vectors, sigma is a scalar.

Terminology! I'm EE as well; I couldn't resist posting to this thread. Now, as you can imagine, knowing all this stuff helps impress the ladies!

All I know is my power panel went bad and I started frying plugs left and right. I never used it again. No matter how careful I was turning it up a little at a time.

Ugh, I just had a "Fields and Waves" flashback.

JUtah, the (only) problem with what you say is that a typical power panel does not drop the voltage all the way from 12 to 1.5 using a load. There is a voltage regulating or step-down circuit of some sort in there. Even my (roughly) 15yr old Tower pannel has a small card of something or the other on the glow driver output, not just a big resister.

The adjustment on the panel really controls a timer that feed 12 volts (yes, 12 volts) to the plug for a short time (a few milliseconds) then nothing for a while; the average value will be what the meter reads. When you adjust the pot, you just increase the time that the 12 volts is on. In short, you are feeding the plug a pulsed 12 volt signal that is on approximately 1/10 as long a time as it is off. If you have access to an oscilloscope you can see this for yourself. The meter is reading the average current of this pulsed signal.

So your saying they are using Pulse Width Modulation Rodney? That would make sense....... and be much more efficient.

O.k...... now for all you E.E's that, much like me, had to chime in........

Mike, absolutely correct...... I use impedance and resistance interchangeably when refering to DC circuits. However by the letter of the law you are correct, as is JNorton who PM'd me with a similar correction

Montague, That would make sense and have been my guess as well. I didn't mean to say that the pot (Knob) on the power panel dropped the entire 10 to 11 volts. Although I can see how my post implies that.

Now I know where the E.E's of the world like to hang out.......



Rich

Yah and we all love RC!

Well I know absolutely nothing about electronics but my power panel sounds very similar. All I know is that it buzzes when connected to the plug and if I put a voltmeter on the outlets it shows 12 volts so I'd guessed that it's exactly what Rodney said, it pulses the power (I nearly said current but I figured the techo types would jump on that ).

However there's one thing to watch out for. Every plug needs a different setting to get the same heat in the coil. I like to have a dull orange glow because this is more than enough for easy starting without overheating the coil. Before I put a new plug in an engine I'll try it out first with the knob turned right down then slowly wind it up until it glows just right then note the position of the needle. I'm certain this is the reason for a lot of 4 stroke backfires and prop throwing...the power is turned up too high which advances the ignition timing.