rx problems

[betty.k]

i m having trouble understanding a problem. i built a tank and installed a 2 channel tx/rx from a toy car. when i had it running with taped up batterys it was running fine. i ve installed a battery holder, and now one of the channels stutters unless the aerials are within 1m of each other. the other channel is ok, unless you run them together (move forward, back), in which case they both stutter in unison. i,ve tried everything i can think oflike using original batt s, tuning that ferite pot, different motors, aerials, the works! i don t know a whole lot about electronics, so i don t understand what s going on or how to fix it. hopefully it s something obvious and simple! HELP!:sad::8ball:

[micro_Amps]

Try moving the motors and the motor wiring as far away from the Rx pcb as possible. Do you have capacitors on the motor terminals? these reduce the rf interference that the motors generate which will cause stuttering and range reduction if they are not there.
Did the toy car have a decent range to begin with?

:)uA

[betty.k]

i’ve got the capacitors across the terminals. originally the range was about 15-20m. today it,s acting strange. the stuttery channel (left motor) stutters when activated on it’s own, but if i activate the right motor the left motor stops stuttering. does this mean a capacitor is playing up?:8ball:

Edited by – betty.k on 10 December 2003 03:08:21

[micro_Amps]

Hmmm, not sure. I know those enertec cars, and you are right the range of those (the one I measured) is 17m.
Was the car originally running on 6v?, I notice you have 4 AA cells there. Increased voltage can saturate the Rx rf circuits.
It might be worth a try using the original motors out of the car to see if that makes a difference.
:)uA

[trash]

Sounds strange, the behaviour sounds almost as if the battery is flat. Or to be more specific, the motor drive circuit is drawing more current than the battery can provide, thus staving the receiver of current. This in turn shuts down the
drive transistor, the available current is restored and the rxer can now turn on again…
thus it appears to shudder.
More current sounds like the answer, but I’m not sure why there is a difference between the battery holder and the original home made pack is.
Did you try to restore the original configuration you had working to see if you could
get back as you had it before.

Tampering with the ferite slugs is just asking for trouble unless you know what it is you’re tampering with. Generally, I don’t, but I own and know how to use a spectrum analyser, so I’m exempt from murphy’s laws of random tampering.

Overall, I think you have some sort of power supply or current drain problem. Sounds more like not enough than too much ?

[betty.k]

thanks for the info guys, i’m a first class newbie in the rc world! i’ve restored the original motors (turns out they have more torque than the tamiya’s!) and moved the aerial to the front. it works a little better, but not as well as the first time. it originally was 3v , so maybe uA is right. but 3v is too weak for the motors so i guess i’ll have to buy something with a 6v pcb. can you guys recomend a relatively inexpensive rx/tx unit with vertical controllers?

[micro_Amps]

Try putting some stronger 3v motors into it.
Ahhh the joys of R&D.
:)uA

[betty.k]

joys indeed! i’m having a ball noodling out these prob’s, just sometimes i’m out of my leage. i’ll hunt down some new motors and see how it goes and let you know. thanks again for the info:D:8ball:

[trash]

Ah, now that sounds a bit better,
sounds like you right uA, the RX board needs 3V and the motors would like 6V. The answer is simple. Dual power rails. 3V for the Rxer and some drive fets with 6V for the motors.
BTW, what are the specs on the fet’s you use.
is the a PDF datasheet for them ?

[trash]

yes, sounds like he’s right too. 3V for your rxer,
and 6V for your motors. Might like to try external drive transistors too. Dual power supply rails etc.

[betty.k]

sounds great but i don’t have a clue where to start when it comes to modding the pcb! i’ve since confirmed this to be true, put fresh batt’s in and halved the range. i guess i’ll have to get 3v motors or a 6v rx. in the mean time i’ll have to hone my driving skills following closely.:8ball:

[betty.k]

hang on a minute! here’s something strange. when it’s running off the battery pack it plays up, but when i run it off a transformer the problem vanishes! so i suspect it needs more current and not voltage, as trash suggested. so how do i get more current? i’m using 4 x AA alkaline batt’s at the moment, what’s the mah rating of this? should i look at getting one of those 6v nicad packs for rc cars? i swear i’m nearly finished with this!:D:8ball:

[micro_Amps]

Hang on a sec, back up a minute……
when you run these kinds of r/c toys on a power pack or transformer the range increases heaps.
This seems to be because the wires that are supplying the power become like an extra aerial and assists in extending the range.
If you are working on this tank idea, stay running on batteries, that will be your best bet to simulate the desired result.

If you want to do dual power supplies, just connect the 4 cells together and take a wire from the middle of the pack (+3v) and run it to the Rx pcb. The wire form the end of the pack (+6v) goes to the motors. Both cicruits are connected to the same negative. What will probably happen (you will have to check this) is that when a motor switches on the terminal on the pcb will go LOW and conduct to run that motor. If the transistor is able to conduct the motor current you will get movement.
If the transistor doesnt go LOW for ON, then you will have to work out another way to run the motors, or change the motors.

:)uA

[betty.k]

so do i remove one wire from each motor and replace it with a 6v wire directly from the batt’s? if so, which wire do i remove? the one that is positive when i push forward? (by golly i’m learning a lot!:D):8ball:

[micro_Amps]

It depends which one changes when you push forward, do the motor wires go positive or negative when you turn the motors on?
:)uA

[betty.k]

not quite sure what you mean by that last post. how do i find out what you mean? i’ve got a multimeter but i don’t understand exactly how and which way current travels around a pcb. i know it starts at + and ends at – but that’s about it. i get the impression that the ic sends the current down both wires depending whether i push forward or reverse, and transistors direct it the correct way out:8ball:

[ph2t]

just to be a bastard here betty, current actually starts at – and moves toward +. Figure that out!

Anyways to your problem:

These motors, where do they connect to? The original PCB from the toy car you pulled apart? If so my bet is that you won’t be able to run the motor in the config above? Why? Because the motor never gets to the Vcc (+ volt rail), it’s switched through two transistors, see below:

In the image above the motor changes direction depending on the current path across it. Red is one path, blue is the other…(ignore the green blocks…)

If you could find where Q6/Q7 in the diagram connect to the Vcc rail you could isolate this and run it at 6V. This way you wold still have the RF circuit and RX chip running at 3V and have the 6V source only tapped into the h-bridge(the pic above) which drives the motor direction.

ph2t.

[betty.k]

uh oh! i think i’m in way over my head now! i wouldn’t even have a clue what a volt rail is, something that comes with a train set perhaps!?:D i can see a whole bunch of transistors but i don’t know what they’re doing or which ones i need to fool around with. know of any good tutorials on the subject, or links?:8ball:

[betty.k]

WOO HOO!!! PROBLEM SOLVED!!!:Di’m such a fool. when i originally pulled the rx and motors out of the toy there was a capacitor across the motor terminals and also a bit of wire connecting one terminal to the motor shell. i left it like this for the initial setup with the sticky tape battery case. when i put it together the second time i removed the terminal/motor shell link thinking “ah that’s probably not important”!! oh how wrong i was! so now, i is one happy diy rc tank with a 20-25m range drivin’ mofo! i’ve learned some valuable rc/electronics lessons now, as you said uA, the joys of r&d! even though it was stupidity that got me into this mess, and pure dumb luck that got me out of it, i can’t thank you (ph2t, micro amps and trash) enough for your assistance on this matter:smiley2::8ball:

ps here’s a pic of the finished product

Edited by – betty.k on 10 December 2003 03:12:31

[merc-blue]

This is what he used if any 1 wants do do this… these r all from DSE
RadioControl Blaster Car $14.98
TAMIYA Twin Motor Gearbox $18.70
TAMIYA Universal Plate Set $9.98
TAMIYA Track & Wheel Set $14.30
total $43.96

hmm might try it my self depending on how much bday money i get..

[micro_Amps]

Good stuff BK. (Where does the user name come from? ) Well done on your project success.
How fast does this little tractor thing travel anyway.?
:)uA

[merc-blue]

yeh can u get much speed outta it.. if soo im gonna build on n let it fly… hmmm construction starts 2 morrow 😀

[trash]

Don’t stop now !!!! Get an extra capacitor and add it to the circuit !!! We’re all on a roll !!! heheheheh:D:D:D

ph2t, the current actually flows from + to -.
The eletrons flow from – to + , but generally most people don’t care about what is going on at the quantum level. 🙂

BK, go out an buy a DSE funway 1 book. (orange book) It’s got these nice little basic electronics things in it like resistors, capacitors, diodes and transistors.

Electricity is just like water, if flows like water.. easier down thick pipes/wires than it does down thin wires.

Current is like the amount of water in the pipes.
the more water you have, the bigger the pipe need to be. The same for electricity.

Voltage is like the pressure of the water.

Resistance is a bit like the size of the pipe.

A transistor is actually a lot simpler than you think it is. It’s is basically a switch.
Look at the 8050 transistors. The line with the arrow is the emitter, the one without is the collector and the one behind the thick line is called the base.

When current flows from the base to the emitter,
it turns the transistor on and it lets (more) current flow from the collector to the emitter.
That’s a nice simple view of how it works and you can get through life with that. Go to uni or tafe and they’ll make it a bit more interesting. 🙂

Edited by – trash on 10 November 2003 20:03:22

[merc-blue]

k heres the plan seeing ur having voltage problems im gonna get Radio Control Thunderfox with Trailer …. its a 6v car and 1.5v car …. ill get the tank with 6 v up and runnign then ill get the 1.5 n build lego tank n c how that goes

[betty.k]

merc blue; actually it cost about $55-60 ( not including batteries or the 2 other enertec blaster cars whose pcb’s i fried!)and i also used the plastic inside packaging from a gummi pizza for a pcb cover! i think it’s well worth doing considering what a ‘proper’ tank of this size would cost. speed wasn’t an issue when i first set out but it putts along at about 2-3 seconds per meter. not real fast but low geared, lotsa torque and boy does it clear obstacles! the gearbox can be reconfigured to an even lower gear ratio and you get 2 sizes of drive wheels. the way i have it set up is the fastest the whole setup will allow without increasing voltage (and we won’t be doing that again, will we!). your biggest consideration is probably the choice of rx/tx. it would be great to get one of those fancy ones that comes in it’s own breifcase but i’m too scared to even look at the price! that’s why cheap rc toys are so appealing. just be prepared to collect a few spare tx units!:Dgood luck!

micro amps; used to work as a dj and wanted a name that stood out (i’m a bloke!) just kept using it when creating a web presence.:smiley2:

trash; aah, so that’s what those little buggers do! likening electricity to water is exactly what i do, so you’re making sense to me. i’ve put together the odd kit, but all you need to know is how to solder and read instructions. i’ll look into a bit of electronics for idiots, see if i can’t learn me sumfink!:approve:

thanks for the support and if anyone tries this project post your results, i’m sure there are plenty of other ways to aproach this one:8ball:

[micro_Amps]

Quote:

ph2t, the current actually flows from + to -…….

hehehe….He may know this, I’m sure it was mentioned in his EE degree

Quote:

Electricity is just like water, etc, etc….

Trash, you and I must have had similar training, I remember this being the first way that I was taught to understand electron flow, all those years ago.

Yeah, BK, I picked you as a bloke, but I was just wondering where it came from. Still DJing?
:)uA

Edited by – micro_Amps on 10 November 2003 23:45:47

[leonli17]

How Fast is the Tank? And I think u can find a cover or a small camera for it.

Edited by – leonli17 on 10 November 2003 23:57:37

[betty.k]

actuallly, ‘tank’ does 1m in about 3-4 seconds. i’ve thought about a camera but the range isn’t good enough to have any real fun (or justify the expense). doesn’t really need a cover, unless i want to drive it in the rain, and the ‘gummi packet’ cover protects the pcb when it flips over. there’s a clear plastic cover on the gearbox which stops dirt fouling up the gears (probably can’t see it in bad quality pic).
not really dj’ing any more, just putting together some tunes at home on the computer. allthough that’s taken a bit of a back seat lately, bitten hard by the rc bug!!:D:8ball:

Edited by – betty.k on 11 November 2003 00:54:42

[trash]

I’m not sure where I heard the comparison to water. Ham Radio has been the best education,
I’d figure you’d probally have tinkered with it yourself uA ?
In the days before internet, CB was the big deal. These days 27Mhz has more SETI traffic on it than local. But it’s still a good place to experiment and learn about radio.

I figure it might be worth writing some simple threads and get the boss to archive them ?

something like ohms law, voltage, current, resistance, power.

resistors, capacitors, diodes, transistors.

magnetic fields

blah blah blah ?

[micro_Amps]

While we are there we might go into some power factor correction capacitor calculations, perhaps fiddle with the likes of Faraday, Lenz and Maxwell, and then stop for a dose of calculus or thermodynamics.
Just kidding, 😀
Good idea.
:)uA

[trash]

Hehehe,
what amazes me is that some clown 300 years ago invented calculus. But the world is a cruel place and his most famous for being hit on the head by an apple !!!!

[betty.k]

great idea trash, i’ll certainly be using something like that if it gets up. when i was searching the net for info on radio controlled electronics, it was either too technical or not there. when it comes to electronics, you can figure out a lot of things on your own (my ‘education’ was f@rting around with audio gear, quite often during gigs! you tend to learn fast when the pressure’s on!), but there comes a time when you need to learn some of the rules, do’s and don’ts, and they’re hard to find if you’re not really sure what to ask for. so a page of links of easy to understand info would be great. be even better if you ‘learned’ guys could write a few tutorials, but i understand you can’t exactly pull something like that out of your aah, back pockets!:approve::8ball:

[trash]

I was just scrolling through the vkham ads a few minutes ago and noticed that one guy has the 2004 ARRL handboks. This may not sound like anything interesting but it is like an encylopedia for radio and electronics. It is a techincal book and it is all hands on deck with some of the maths, but at the same time it covers the basics than anybody can understand. It’s about the size of a phone book. DSE sell them too if you want to actually have a look in one.

They are a book that the average person off the street wouldn’t read, but would suit somebody like betty very well. As you learn more and more, using this book as a reference will bring you up to speed very easily.
If the DSE funway 1 or 2 book just doesn’t have enough info in them for you, ask santa for an ARRL.

They update the book every year, but my 1988 book is just as good as the 2004. They will last you a very long time.

http://vkham.jbo.com.au/cgi-bin/classifieds/classifieds.cgi?search_and_display_db_button=on&db_id=14883&query=retrieval

I’m constantly learning new things.
Today we destruction tested LED’s.
How many volts can a LED take before Pfffffft !
Can you make a green LED glow red ?
What happens to a UVEPLA chip when you program it with a capacitor 2000uf charged to 60V.
(adds new meaning to burning a EPROM)

[betty.k]

thanks for the book tip!
for a while there i thought i had a few orange led’s until i realised they were over powered green ones! i also remember playing with a friend’s power supply unit and melting a few led’s, lotsa fun!:D:8ball:

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