More Adventures In Electronic Land or How to Make Wires Smoke!

Hey, granted I'm working In the dark (darkness of ignorance) .... but I have found tinkering with these electronic gadgets to be fun and not something to be afraid of. Oh yes, I take precautions. I use old or unused batteries, not my new 7 channel transmitter and I burn up a part or two once in a while, but I am learning by making things work and my new text books are then much easier to read and understand. Is there a private pilot out there that enjoyed ground school more than air time? Yet air time makes ground school, translated 'book work', easier to learn, right?

This is not the easiest, certainly not the cheapest way to accomplish my desired ends but I don't want to just 'charge longer'. It is important to me that I know what is happening and that I have control of it. The Manufacturers have to assume consumer ignorance and set up safe perimeters for self protection. For instance Futaba's 'G' series transmitter has an in-line fuse that thwarts any rapid charge that will harm wiring. The 300 ma (not 3A as labeled) fuse has been a problem for me as my new 250 ma fast rate charge has an initial surge of a little over 300 ma. This causes a blown fuse every time. The fuse works great for Futaba's purpose though, that of light 29 gauge wiring. I think our interests could better be served by use of more substantial wiring and making high rate batteries a standard feature in all equipment. I for one would be happy to pay the extra cost of the few pennies they are saving. We all know how the prices of equipment has come down over recent years and all the 'whistles and bells' have almost become standard. I have heard and experience has shown that equipment is 'more reliable', but is it better? Does the American Way have to be glitter at the expense of guts? Whew, don't that twist your tail?

So! Now I'm working on a variable rate charger and starting at a low rate, I can then crank up to the desired rate, hopefully as much as 500 ma on everything but the Futaba. I'll have a meter for charging rate, (millimeter) and an ESV, (millivolt meter), to Indicate battery voltage. Make it AC/DC and with a 'load' feature and a variable charge from about 100 to 500 ma and you've got it all, right'? Well, how about charging both transmitter and flight pack at the same time; a meter for the DC power source, hell, I'll have to box it in a footlocker! The DC source meter doesn't sound serious, huh? What if that 5 yr old motorcycle battery only has 8 volts in it and that 9.6 volt transmitter has been flying for a couple days? "You cannot push water uphill", (old Norwegian proverb!). Meters alone more than double the cost of my endeavors but I feel they are necessary so I can 'see' what is happening. The speed and movement of those needles can be the most important indicator you have and I highly recommend many hours of playing with your new toy before you do anything serious with It. The experience gained can be very valuable. For Instance If you plug into an old high resistance battery that you know needs a charge, you could crank up the amps but if that needle doesn't start moving up fast, with a little experience behind you, It is quickly evident that you have a problem. By the way, do you need some new high rate cells? I have heard and read numerous recommendations to use Sanyo batteries, both red and yellow label. The red label battery has a higher discharge rate than the yellow and give up its power at a faster rate therefore, but with a shorter duration than the yellow version.

I'm sure there are experts out there that take exception to what I am doing, saying or spelling but hopefully this could prompt some response that could be helpful to all of us. The answers to my questions are kind of slow in coming so I for one can use all the help I can get!

For instance, I want to know how much power I'm using up in a flight. Then I could put back just what is necessary with the timed charge. Sure, I can get a good charge, fly a couple average flights then discharge to see how much amperage has been used up, but here again I need to know the load the discharger used compared to flight load usage, charge rate on that manufactured charger (some don't have it!)..., isn't there an easier way'? If a couple 10 minute flights with a smaller 'full house' model requires as I have read, about 15-20 mins. at a charging rate of about 250 ma to replenish the charge. How would that translate into large scale usage, with twice as many and larger servos? A 250 ma charge for 2 hours replaces 500 ma, 1/8 x 500 (15 min./120 min. x 500), = 62 ma or about 30 ma for one flight of 10 minute duration. If large scale uses twice the power per flight, this could be some useful information.

Early In my L-4's career I used a Kraft 500 battery pack and the 4th flight would be terminated when aileron servos ceased to function on long extension leads and I would have to rudder and elevator the sucker to a swift landing. That would indicate that just 6 KPS-15's used over 100 ma per flight. Of course, I never let that poor L-4 go straight and level for very long.

Okay then, how about an ESV for 1200 packs. How much of a load would be indicative and useful? Is there a modification that could be made or added to existing chargers for large packs so charge time for transmitter and receiver pack would be of equal duration? Is there a formula that would determine how much in put power is necessary to charge receiver and transmitter at the same time? How about two receivers and transmitters or a number of receiver packs?

Dumb questions? Maybe, to some, but there are giant scalers with more than one plane. In my case the ideal charger would be AC for at least two transmitters and two 1200 ma packs at the same time with a DC capability for field charging at least one or the other at a time. A charge rate that reduces or switches to 10 or 20 ma for a trickle rate would be highly desirable In AC mode so everything could be left plugged in and ready at a moments notice. How about a variable rate to slow things down for high resistance batteries? Is this unreasonable? Hell, I don't know but I'm going to find out! It will be my stumble along way unless I get some help but I don't want any 'charge longer' answers!

I have purposely left out specifics about what I am doing as there are many hidden dangers and I am sure I don't know all of them so I'm treading very softly. Hopefully this disertation will pique the interest of others and get you to at least question what is going on in those 'Little black boxes'. The more you understand the better you will be able to determine if they are really doing the job you expect of them. If you enjoy or would Like to learn more about electronics, there are many useful kits available from Ace R/C, Heathkit and others I'm sure, If you want to put things together and see them work. My problem is that I want to know how and why so, 'solder A to B' doesn't do it for me. If you are like me I would recommend using manufactured kits and buy a couple books - learn what's going on and that knowledge can keep you in the air with everything whole and therefore safer. I'm hoping I get back some info from you readers. Let me know what you expect and desire from our electronics and you experts can let us know how to get what we want! Feed back from discussions while just writing in this column has given ideas on another way to go with a good fool proof charging system that would work for any and all! Interested?

Babe in the Woods of Electronic Land

You buy a new radio, mount it in your new giant scale model but substitute a 1200 ma battery following recommended practice. Everything is given a good overnight charge with the brand new charger and you are ready to go, right? WRONG! Of course not, If you know what is going on. That new charger is usually a 45 ma rate or similar. At the 'normal' charge rate of 1/10th capacity of the battery, in 10 hours a 450 ma battery will be fully charged from a dead condition. But now you giant scalers have a 1200 ma battery with only 450 ma in it - just over 1/3 of a charge and a feeling of well being simply because you have a large battery on board. Everyone knows better and doesn't make this mistake right'?

By the way, new batteries should be charged per instructions. First time or 'initial' charges have extended, usually 16 hour charges and, experience has shown me that those new batteries are not flyable (spelled 'reliable'), until charged and discharged at least three times, allowing about 24 hours between discharge cycles.

Anyway, a 500 ma battery is not usually completely dead and a 45 ma rate for 10 hour charge is plenty, but now with the big 1200 ma pack you ask your local electronic expert what to do and he just says "Charge the 1200 ma pack longer". Did you realize that 'longer' is two whole days'? We, as giant scalers, have a number of such problems and although I pour through all the magazines, I find no one addressing any of these problems. If a new, somewhat isolated giant scaler tries his hand without knowledgeable help, he is in trouble, right? Absolutely no one is more ignorant than I when it comes to electronics so my rambling about my electronic endeavors is far from technical and only meant to spark interest. Hopefully the unknowledgable will question automatic answers and want to know what is really happening in our little black boxes and the experts will realize that there is a void between 'common' practices and the necessity of some alterations of those practices for giant scale use.

When I first started using large capacity batteries, I made up my own packs for odd but matched high amperage batteries of unknown capacity. I was flying with the batteries and discharge tests would show over 2 hours of capacity left by just charging 'longer'. What a surprise to find that if properly charged, a discharge test would show over a 4 hour capacity! Here again our specialized interest is divergent to 'common practice'. Our timer discharges are under a load to simulated 'useful' capacity left in our battery but not the giant scale machine with heavy duty servos which use more power and twice as many are used! Should higher capacity batteries have a larger 'load' for duration or expanded scale voltmeter (ESV) checks? I think the checks would then be more meaningful.

Recently manufacturers have produced a number of electronic goodies but interests and desires are so varied In the modeling community, that it is next to impossible to find exactly what suits your purposes. At least this has been the case for me. What to do?

While on a recent visit, good buddy Bill Wendt listened to my complaints of battery charging problems. Half of them didn't work or took forever to do anything with big packs and sure as hell cannot plug into the desert sand of Las Vegas! Bill promptly offered to help build a charger to do what I wanted. How's that for a friend? The result of our endeavor is shown here...

Look at all those switches and lights!

From the left: The 1st vertical row is the dual rate switches. The next row, meter switches to monitor chosen circuit. Below the meter is the 'AC, Off, DC switch and the 'On' indicating LED. The next row is LEDs, Red for Hi-rate and green for Lo-rate charge. The last row is charging jacks.

How does this look for a pile of Radio Shack parts and about $75? Now comes the good part! The charger features a metered dual rate, AC/DC, for two transmitters and two receivers, 1200 ma size! At the low charge rate, all can charge overnight at a 10 hour rate. Trip one or a bunch of switches to hurry things along at a 250 ma rate for about 4 1/2 hours on a discharged battery pack. Of course Bill did all of the heavy (thinking) stuff and I just got to solder wires and punch holes but it stirred my interest enough to want to try some stuff on my own.

Electronics have always fascinated me but my education is sadly lacking in that department. I've noticed in my trusty Radio Shack catalog that they had regular text book courses on basic electricity. So, I now have 'DC Circuits', Vol. I and Vol. II, ($6.95 ea.) and 'Electronics Data Handbook', ($1.95). The two volume course was developed and published by Texas Instruments for Radio Shack as well as use in their own Learning Center. The handbook is a reference book for laws, formulas and definitions. Now I'm learning the difference between schematics and road maps! I've always been an avid reader of electronic columns such as "Electronics Corner" by Eloy Marez In Model Builder and 'how tos' such as "Dual Rate Field Charger" by Clay Howe, (RCM, 7-'82), the Auto Tester article by Jim Bigley, (MAN, 9-'83), 'Electric' columns by Bob Kopski In Model Aviation and of course Jim Oddino is back with us In RCM again.

Well, I got my bravery up and tried some hands on building for myself. The first endeavor was an expanded scale voltmeter per Mitch Poling's article (MB, 5-'83), and it worked! The meter is intended to monitor battery voltage during fast charging of 6-cell battery packs but I was able to adapt it to suit my purpose easily. Voltage is limited to the meter by a 'Zener Diode', a one-way limiting valve so to speak, whose 'value' determines what voltage shows up on the meter. For example, a 9.1 Zener Diodes use means the meter will only register at a voltage higher than 9.1 volts. This was fine for transmitter batteries but what about receiver packs? Well, just stuck the 9.1 on one side of a double pole switch and 3.8 on the other and both diodes were joined in series to the meter through a potentiometer (adjustable voltage 'faucet'), which determines needle deflection on the meter. I went so far as to buy a 'digital' multimeter to use to calibrate my ESV/charge monitor. By applying a known voltage to the meter, you use the potentiometer to set the needle deflection where you want it, the more deflection the better. Next the plastic meter front was removed and existing numbers were painted out, a '0' was 9.1v, right? I then took a pair of 500 packs to simulate a transmitter that needed a charge, hooked in the ESV and my multimeter with jumper wires and turned on the charger. As the battery was charged up, I made notes of the voltage shown by the multimeter which were then logged on the ESV meter at the appropriate locations. Two scales were calibrated in this manner for both 8-cell and 4-cell packs.

Great! I can now monitor charging and have a plug-in ESV battery checker but the checker does not 'load' the battery yet. So, that's next. It's back to the Lab and hook some resistors into the voltage circuit to be engaged by a push button to 'load check' the batteries.

A load check is a necessity as even a tired nicad will indicate near full voltage but when it has to work, the battery weakness will be indicated by a rapid needle drop on the meter. A good or charged battery will 'hold' it's voltage level with only a slight or very slow needle drop.

Well, this is getting long so we will continue in the next installment of 'Adventures in Electronic Land' or 'How to make wires smoke'.

The Smoke Clears (?) No but it is thinning out! Hey! I'm learning! Besides that I've conned my local electronics expert, George Steiner, to answer the dumb questions I come up with. I'm sure you recall that George was designer of the 2x5 'redundant' battery system that Ace R/C markets. Lately he designed a field charger, called a 'Super Juicer', (RCM, 6-'83), but trying to get one out of George is like pulling teeth! He does have a PC board and parts kit available, GSP Products, 2238 Rogue River Dr., Sacramento, CA 95826. I'm trying to get him to add a transformer to give AC capability also.

While telling George what I've been up to he explained a couple things that have me now going in another direction. My next adventure was to use a 12 volt source for charging 8-cell packs and a 6 volt source for 4-cell packs. Remember that 'Old Norwegian Proverb'? You have to have a higher source voltage than your receptacle. The low resistance of a nicad allows an in-rush of power from the source battery in an attempt to equalize the voltage and cannot 'over charge' your battery pack. Use an Expanded Scale Voltmeter, (ESV) to monitor the charge and use the rise of the ESV needle as an indicator to stop the charge. When the needle stops, you take on a lot of power at a high rate, accompanying will be a bunch of heat. A low or dead battery may well cause excessive heat. This can be controlled by slowing down the charge process with a variable resistor such as a large wire wound potentiometer or a small 'Variac'.

I would expect the capacity of the source battery to diminish and charge time to lengthen but depending on capacity (amperage) of the source battery, a number of charges would be possible. A well charged source of 4 to 6 amps should be ample for 2 or 3 charges and 2 or 3 days of flying. The higher the amperage, the more charges possible. I would envision the chargers use as a top-off charger daily after a good slow charge prior to weekend flying trip of 2 or 3 days. This would eliminate concern about availability of power at the flying site or the need of a generator or 'inverter' (DC to AC converter).

What about adding AC capability for home use? What would be wrong with a road racing or train transformer of 13 to 16 volts, 2 to 4 amps? In this case I feel meters and a bit 'pot' (potentiometer) to be a necessity. Get your parts from yard sales and flea markets. Find a good transformer in a useless road race game, a 50 mv (millivolt) meter and a 500 ma (.5A) to 1 amp meter, some wire and Zener diodes and box from Radio Shack. Feasible? Just look...

Adjustable from 200 ma to about 1A, metered, unplug AC plug in DC and it becomes a field charger and can even charge my 12 v source battery! You can regulate the charge and if you have hi-rate cells you can 'dump charge' like the electric car pilots do. They run their batteries way down and 'dump' in a 15 minute charge sometimes at 4 to 6 amps! Talk about heat and smoking volt (ESV) meter go up. When it slows and stops, terminate the charge. No muss, no fuss. Boy, I can just hear the hackles raising on the necks of the experts! I hope so, I want to hear about it though. I am quite aware what I am doing and saying is against good practices. I know that 'dump' or high amperage charging is going to ruin batteries and can be unsafe for equipment. That's why I'm not drawing diagrams for anyone to follow. If the interest and desire is there, I've enumerated sources that anyone can learn what to do. To do this, they will have to learn and understand a little about what is happening, same as I did, right? I want this dissertation to be a little controversial not a construction article.

So, what if I do ruin my batteries in 1 or 2 years? I am watching and paying attention to them. I'll know when something is not right and don't have to trust a sealed black box that the LEDs don't work right on. I am a lot more comfortable and knowledgeable with my batteries and therefore am a safer pilot as well!

Speaking of replacing batteries, 'R-Car' 1.2A high rate cells were designed for electric car use. They come tab welded in pairs, 'In the plain gray wrapper', perfect for fast charging and are inexpensive, 8 for about $21. Can't beat that!

Remember the fuse in my Futaba transmitter? I thought my charger was blowing it? Well, 'taint so. Sitting and cussing, I recalled that Bill Wendt told me to plug things in before turning on the charger. It seems that banana plugs cause a momentary short every time they are plugged in. So, I blew a couple more fuses with the charger off and unplugged before I realized that it was the transmitter battery blowing the fuse! I use interchangeable pigtails and Deans Plugs so all I had to do was to plug in the banana plug before connecting any equipment. No more blown fuses. Great, dummy! Now I'm looking for something like the Futaba transmitter charge plugs to replace all banana plugs.

Are ESV's useful? Yes and no. Yes, if used as an indicator and not if used as a fail safe. The discharge curve on nicads is very flat not straight downhill like dry cells. If you are close to the end of that curve and near the sudden drop off, an ESV can show you have useful voltage but a one last flight might be all it takes to put the batteries over the down side of the curve.

So, what would work for a meaningful ESV load? How about a meter, a switch that doesn't stay in the 'on' position but gives a momentary 'dead short' condition. Deflection on the meter is your indicator. So, what size meter? Would you believe at least 60 amp? Yep, I'm told nicads with their low resistance can really put out. You could calibrate the meter with a green area. Determine high and low by using a battery good for only one 'last flight' and a well charged pack to set the high mark. Sound okay? I haven't tried it yet (scary!), but it's on the agenda unless I'm told otherwise. Smokin' wires here I come! See, my soggy underwear is not from fright - Just a fire prevention measure!