RC battle ship, simple questions

[Dragon Tamer]

I was thinking of making a scale working model of a WWII battle ship (I haven't decided which one yet, but the Bismark is a good candidate).

There are just a few questions that I had and was hoping that someone could help me.

My first question, I wanted the transmitter to operate at roughly 4MHz because both the transmitter and the receiver use a 4017 as the channel selector and since the 4017 has a max frequency of 5MHz. Do I need a carier frequency or can I just transmit the 4MHz directly?

Second, if I do need a carrier frequency, which do you recommend AM or FM carrier? I know that most modern RC transmitters use FM coupled with a crystal to control frequency.

Finally, I wanted to add a simple sonar to the model to find out if it's heading into shallow water. What I was going to do for this was an array of simple circuits operating at a 10MHz frequency. I've attached a schematic, if someone could just look over that and tell me if I got it right.

 

[Dragon Tamer]

So am I to understand that nobody has an answer for me? I thought this was a fairly simple question.

 

[Boncuk]

Hi Dragon Tamer,

may be your question is simple for you - it's not simple for me, and obviously not simple for other forum members.

So how would you control a battle ship using sequential control (via a decade counter)?

Before you are through with a sequence your valuable battle ship could ram a quay and sink. Secondly, how would you stop the 4MHz clock in time to have the counter stop?

Also the 4MHz you were talking about is just the frequency you use to clock the counter. There is some distance between you and the ship which must be overcome by some means of data transmission.

A general way for R/C model control is using an R/C set consisting of transmitter and receiver with connected servos.

You might think about using modulated IR, which requires to have the model in sight at all times, an omnidirectional IR-receiver and an IR transmitter strong enough for several hundred meters range. (Be prepared to carry a truck battery for transmitter operation. )

Multi channel R/C sets are affordable nowadays other than in the early 70s, when I had to pay 1,800DM (Deutsche Mark) for a 14 channel digital proportional R/C set with seven servos, deducted by 40% for export. (normal sales price 3,000DM)

Remark: 2 R/C channels are necessary to control one function, e.g. rudder left and right.

BTW, under no circumstances mount a 38colt in the alpha turret of your battle ship. A friend of mine almost shot a pedestrian doing that with his "Bismarck".

Regards

Boncuk

 

[Dragon Tamer]

So how would you control a battle ship using sequential control (via a decade counter)?

The idea is to have the decade counter in the transmitter select a pot in series with the 4MHz crystal, the pot would modify the amount of time that the crystal takes to charge slightly causing different time constants for each output of the receiver decade counter.

Secondly, how would you stop the 4MHz clock in time to have the counter stop?

I'm not sure what you mean by that, but I did notice that I had forgotten to add an important circuit to the transmitter. The circuit would prevent the 4017 from resetting until it received a signal from the model that would be transmitted once the models 4017 output 9 goes high, it would then allow the transmitter to reset. That way if the model went out of range the transmitter and receiver would not fall out of sync.

Also the 4MHz you were talking about is just the frequency you use to clock the counter. There is some distance between you and the ship which must be overcome by some means of data transmission.

So how would you recommend I go about doing something like this? All of this is completely new to me.

A general way for R/C model control is using an R/C set consisting of transmitter and receiver with connected servos.

But then I could not brag that I made the whole thing by myself and from scratch

You might think about using modulated IR, which requires to have the model in sight at all times, an omnidirectional IR-receiver and an IR transmitter strong enough for several hundred meters range. (Be prepared to carry a truck battery for transmitter operation. )

I've had some experience with IR in daylight and that lesson tought me that the receiver will not be able to receive commands because of the bright sunlight overwhelming the receiver.

Multi channel R/C sets are affordable nowadays other than in the early 70s, when I had to pay 1,800DM (Deutsche Mark) for a 14 channel digital proportional R/C set with seven servos, deducted by 40% for export. (normal sales price 3,000DM)

True, but that brings me back to my earlier point of making it from scratch just for fun and bragging rights. Also, I recently took inventory of all of my integrated circuits and I have about 45-50 4017s (each time I count I get a different number) so I thought it would be a good idea to use some of them up.

Remark: 2 R/C channels are necessary to control one function, e.g. rudder left and right.

I thought it was only one for the rudder.

BTW, under no circumstances mount a 38colt in the alpha turret of your battle ship. A friend of mine almost shot a pedestrian doing that with his "Bismarck".

I was designing mine to work with 22 cal blanks.

 

[canadaelk]

DT: "But then I could not brag that I made the whole thing by myself and from scratch"

Your mom could not claim that either when she baked bread. She did not grow the wheat or thrash it. She did not draw the water or load the stove with wood. So give me a "from scratch" example please. E

 

[Vizier87]

DT: "But then I could not brag that I made the whole thing by myself and from scratch"

Your mom could not claim that either when she baked bread. She did not grow the wheat or thrash it. She did not draw the water or load the stove with wood. So give me a "from scratch" example please. E

I think he meant pretty well when he's using ICs rather than buying whole RF PCBs with built in I/O pins. A bit of tact in replies would be nice.

Cheers.

 

[Sig239]

Hello Dragon Tamer, I haven't studied your schematics in great detail, however based on what you're saying, it sounds like you don't fully understand the basic building blocks of FM, AM, or R/C. The good news is, you can use your 4017s to make the Encoder portion of the transmitter and the Decoder portion of the receiver. Unfortunately, that is only one of several building blocks on either side of the equation. The ARRL handbook is a great place to start learning. You can find the ARRL Handbook in the reference section at the library if you don't want to fork over the ~$40 to buy it.

Harry Lythall - SM0VPO has a great homebrew page with a nice encoder and decoder using the 4017. The encoder and decoder simply takes care of the timing and multiplexing of the individual channels, it really has nothing to do with the rf portion of the circuit. I'm in no way trying to discourage you from building it, you just have some studying to do. In fact Harry even suggests using the ready made radio modules for the rf portion of the setup and you can still build the encoder/decoder portions using your 4017s.

 

[Dragon Tamer]

I have the 2003 ARRL handbook, which is where I got the idea for the transmitter. Unfortunately the handbook doesn't go over RC with much detail. But it sounds like your suggesting that I establish a carrier frequency for the transmitter to carry the 4MHz signal. That confirms what I originally suspected, unfortunately most of my RF projects don't work at all, and only a few work well. But I'm still going to try.
So if I want to use an FM signal I want the frequency to be at least 3 times higher than the clock frequency right?

 

[Sig239]

LOL!! Forgive me, but you are in way over your head! Scrap the whole 4MHz idea. The 4017 would only be operating with a 50Hz clock. This is the refresh rate of the servos. Read up on pulse position modulation or PPM.
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The R/C section in the ARRL handbook tells you everything you need to know about how to create the signal to be sent. The REST OF THE BOOK tells you MOST of what you need to know to make the transmitter and receiver. Read each section until you understand all of it. What are your previous working RF projects?

BTW, did you check out the link I posted previously? Also check out the RCGroups forum. Personally, I think you should buy hobby grade radio equipment and concentrate your efforts on the building of the boat. You can get plenty of "street creds" for making a kickass boat, but this is an electronics website so I digress.

You need to choose a frequency suitable for R/C cars and surface vehicles only. DON'T choose a frequency meant for R/C aircraft or small errors in your design may cause other peoples air planes to crash into your skull. Perhaps 27.045 MHz would be a good choice. That would be your carrier frequency.

Then you can decide if you want to modulate the amplitude (AM) of the carrier or the frequency of the carrier (FM). AM may be the more simple of the two. You'll need a 27.045 third overtone crystal oscillator, a buffer amplifier, and a half watt power amplifier. Each stage must be tuned to your carrier frequency.

Then you use the PPM circuit referenced in my previous post to turn the power to the buffer amp and power amp on and off (this is 100% "down modulation", a simple form of AM). Do you have access to a scope to view the waveforms you intend to generate? You must generate a clean signal. How about a spectrum analyser? frequency counter?

Have you ever made a High Frequency oscillator? Don't forget to read the Handbook and follow good rf design practices. Maybe some of the radio guys can give you some more pointers. Let me know when you get done with the transmitter, then we'll talk about the receiver.