remote control system built with discrete components, chips

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remote control system built with discrete components, chips

Post by jackbbot » Fri Nov 30, 2007 8:02 am

Does any one have an idea how to build a basic remote control system
without buying a kit or special rf modules?? Or a book or website with a thorough tutorial on how to remotely control relays, motors or servos??
Prefer to construct using basic components available ubiquitously?? What kind of circuitry is involved for the transmitter and receiver?? How does the whole thing work??

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Post by jwax » Fri Nov 30, 2007 4:07 pm

Welcome jackbbot! Sort of depends on your level of expertise. Not knowing how a receiver transmitter link works puts you at a disadvantage. What is the end result you're after? A demostration? An actual practical device? Or just a learning experience?
The link can be rather simple or complex depending on your objective.

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Post by Dean Huster » Fri Nov 30, 2007 5:19 pm

Can't think of any reason why you couldn't build one using TTL, CMOS and/or analog ICs or even discrete components. With discrete components, you'd probably end up with something the size of a large table radio and with ICs, maybe something the size of a brick. Basically, you'd be using an EPROM or two driving some digital gates that allow timed bursts of 40KHz to drive an IRLED.

For that matter, if you want to really get nutso, I suppose you could build one using vacuum tubes and end up with something the size of a 5-shelf bookcase for your remote! Maybe a case of the tail wagging the dog in most cases.

Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).


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Post by MrAl » Fri Nov 30, 2007 6:49 pm

Hi there,

I would have to ask, what aspect of the design are you most interested
in, the rf design, the signal generation design, or if you just want
to use IR instead of rf?

The reason i ask is because there are modules made up that transmit
and receive rf and all you do is add the microcontrollers and you
have an rf link. If you want to design the transmitter and receiver
then you are in to rf design as well as the design of whatever is
required to generate the signal (audio, digital).
LEDs vs Bulbs, LEDs are winning.

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I like Dean's idea>> what would that circuit look like

Post by jackbbot » Tue Dec 04, 2007 10:56 am

To answer some questions such as jwax and AI the system of interest would use R.F. not infrared. The ARRL handbooks are not that detailed
on this subject just a page or 2. So in terms of background>>

familiar with F.M. and A.M. concepts although the only receivers built
so far are bought as kits, have not yet completed own receiver transmitter
design>> reading ARRL handbooks to try and do this

familiar with mathematics of the signal representations / modulation from
2nd year in electrical engineering

but do not really know what this thing would look like

would the circuit differ if it engages a relay as opposed to a servo
or maybe that is redundant because maybe the relay already controls

like dean's idea with I.C. s brick sized unit

do have an eprom programmer so that is a plus

but need circuit schematic of demo circuit to see what the thing would
look like

then eventually move on to modules and microcontrollers to minimize the size further

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Post by haklesup » Tue Dec 04, 2007 11:38 am

Sounds like you want to build a 1970s-80s vintage RC car toy controller. The old one channel RF type that let you back up turn right at the same time. All you could do is drive straight and do three point turns.

They were true discrete designs with no ICs. The transmitter was about 2x3inches and the reciever was about the side of 2 D batteries on profile (~2.5"x2.5"). Plenty of transistors and passives and tunable RF chokes. Parts that are a bit harder to get these days.

I only recall one and two channel controllers with just one or two buttons. I get the sense that a more complex control system (like variable stearing servo) would require a lot of PC board space if you stuck to just a discrete design.

These older controls were just on-off signaling, no data or analog signal was encoded with the carrier. The reciever only had to detect a carrier at a particular frequency, it did not need to decode a signal like a radio would so it could be simpler. In a way the transmitter would have been like an AM transmitter without the signal mixing section, just a carrier wave. two channel transmitters were just dual versions of the above with two different carrier frequencies.

I suggest you look for a vintage RC toy or the guts to one in someones junk box and then reverse engineer it. In most cases they were two layer boards and thus would not need to be torn apart to reverse. I seem to recall one in one of my junk boxes, Ill look and post pix if I can find it.

Somewhere along the way there were hybrid designs with some ICs to do the complex stuff and some discretes to do the mixing and switching. Now there are fully integrated designs that require only a few caps or coils externally to operate. Today toys use a single carrier wave and modulate the control signals (digital or analog) onto it where they are decoded at the toy and sent to the control relays, fets and motors. These are true radios. A tranciever simply employs both the transmitter and reciever circuits in one place.

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Post by jackbbot » Mon Dec 10, 2007 9:03 am

Does anyone have a circuit schematic for the parts involved?? What would it look like??

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Post by Sambuchi » Mon Dec 10, 2007 11:27 am

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Post by philba » Wed Dec 12, 2007 12:57 pm

check out these guys - they sell pretty much every thing you need and have plenty of ap-note type docs here . Of course, you can always build it with discrete components.

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How about using InfraRed?

Post by gmclam » Fri Dec 14, 2007 7:15 pm

I'm not sure what "medium" you want to use - RF, InfraRed, UltraSound or something else. Remote controls for garage doors are usually RF, while home electronics use IR these days. IR stuff is plentiful and cheap. You could easily build the transmitter half from one of dozens of ICs available (or just buy an old 'junk' remote from the local GoodWill).

On the reception side, Radio Shack (of all places) has part 276-640 which will receive the IR, filter it, and provide a TTL signal. Connect the TTL signal to a PIC (or CPU of your choice) and do whatever you want with it. Software in the CPU measures edges of the signals to capture the bits. There's a lot of documenation on the web about the few IR protocols in use.

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