Hi everyone.

As I had mentioned, I was not able to complete not only the tests for the "low battery warning and automatic replacement of the reserve battery" circuit but I did not even carry out the tests to make the transition from switching from 6 to 12 volts less sudden on this circuit we are dealing with.
Unfortunately, while working on the table in the living room, I had to clear the table before my wife did it independently but much more drastically.
Unfortunately I don't know when I will be able to do these tests again.

In the meantime, I wanted to ask you for a technical opinion.

Could a coil in series (logically not in parallel) on the 12 volt circuit produce the effect I want?
I was thinking, trying to remember the laws of physics, in particular what the great Russian physicist Lenz passed down to us.
The coil should oppose the variations in magnetic flux, in the moment of passage of the current in the first moments it should create an induced current that opposes it.
I was wondering whether this scientific evidence can actually produce the desired effects and, in this specific case, which type of inductance to use. For example by how many milliHenry?

Good evening everyone.

As I had previously anticipated, I will explain how this simple circuit works, for those who are interested because they want to make it or out of simple curiosity.

The first diagram is simpler, it is used to understand the logic of operation, there is only one relay equipped with four contacts.

The second scheme is the one I actually used having two relays available.


UNDERSTANDING THE TWO PHASES OF THE CIRCUIT

COIL NOT ENERGIZED

In the first image (simplified diagram with a single relay) you can see what happens when I operate the radio control lever in forward gear.
In this case the current flows in the coil (which has a circuit [electrical mesh] in parallel with the ESC) but the voltage is not yet sufficient to excite it.
If the coil does not energize the contacts are not activated (i.e. modified), therefore the "normally closed" contacts will remain closed and the "normally open" contacts will remain open.
In this condition, only the current from the ESC circuit will reach the motor.
The conventional direction of the electric current (not real electrons) from the positive pole to the negative pole is displayed by the arrows.
The large arrows (red and black) indicate the ESC mesh current, while the small arrows (red and black) indicate the current path in the coil.

In the second image (simplified diagram with a single relay) you can see what happens when I operate the remote control lever in reverse.
Due to the diodes placed only in the electrical mesh of the coil it will not energize.
The conventional direction of the electric current (not the real one of the electrons) is visualized by the arrows.
The large arrows (red and black) indicate the ESC mesh current which is reversed compared to the previous situation.
The 12 volt circuit will not be able to operate even at the maximum negative voltage that can be delivered.

In the third image (real two-relay diagram) you can see what happens when I operate the radio control lever in forward gear.
The situation is the same as that of the first image but more faithfully reflects the practical tests recorded in the attached videos.
Measuring instruments (voltmeter in parallel and ammeter in series) and fuses have also been added. In the simplified diagram they have been omitted to facilitate understanding.

COIL EXCITED

In the fourth image (simplified diagram with a single relay) you can see what happens when I operate the remote control lever in maximum forward gear.
In this case the current flows in the coil (which has a circuit [mesh] in parallel with the ESC) and the voltage is sufficient to excite it.
If the coil energizes the contacts are activated (i.e. changed), so the "normally closed" contacts will open and the "normally open" contacts will close.
In this condition, only the current from the 12 volt battery circuit will reach the engine.
The conventional direction of the electric current (not the real one of the electrons) is visualized by the arrows.
The large arrows (red and black) indicate the 12 volt mesh current, while the small arrows (red and black) indicate the current path in the coil.
The circuits are not in parallel, they are galvanically separated.

I omit the complex two-relay scheme for reverse (it is superfluous).


In the fifth image (real two-relay diagram) you can see what happens when I operate the radio control lever in maximum forward gear.
The situation is the same as that of the first image but more faithfully reflects the practical tests recorded in the attached videos.
Measuring instruments (voltmeter in parallel and ammeter in series) and fuses have also been added. In the simplified diagram they have been omitted to facilitate understanding.


PROBLEM OF THE CORRECT COIL EXCITATION THRESHOLD

The theoretical operation has been described so far, but in reality there is a problem. I thought of solving this problem by placing diodes on the electrical mesh of the coil.
What's the problem?

The coil is nominally 6 volts but in reality it is able to energize (electromagnet effect capable of modifying the electrical contacts) with much lower voltages.
In this way the system will still work, but the excursion of the lever in forward gear will be very reduced, because it will be enough to raise the voltage on the coil by a few volts to energize it and trigger the 12 volt circuit.
Thus we could not exploit the entire 6 volt range (or slightly less) available.
Placing the diodes in series before the coil causes a voltage drop.
Yes, I'm not using diodes in the most classic way but I'm exploiting them for another feature.
Each diode has an electrical voltage drop across its terminals (if I remember correctly these have a drop of 0.7 volts).
By increasing this voltage drop it is necessary to supply more voltage to energize the coil. The coil will not energize right away.
The more diodes I put in, the more voltage is needed to excite the coil.
In short, the more diodes I put in, the closer I get to the maximum threshold of 6 volts, exploiting the entire range before the circuit switches.
To understand this, remember that the diodes are placed on the coil circuit only so their overall voltage drop will not cause any effect on the voltage the motor receives.
What happens if the voltage drop is too high because I placed too many diodes?
It simply will never energize the coil and never switch the 12 volt circuit, so I have to gradually remove a diode to gradually reduce the voltage drop.
With these small adjustments I find the ideal threshold.



REFERENCE AND EXPLANATION OF THE VIDEOS

In all the videos you can see the test of the two relay circuit.

You may notice that there are three multimeter testers.

The first blue tester on the left is used as a voltmeter (see the diagram in the sixth image).
It is connected directly to the motor so it will detect the voltage that reaches it. Just by looking at this instrument we will be able to understand which circuit we are using.
From the number of volts we will understand (as well as from the obvious change in engine speed) which circuit is working, at 6 or 12 volts.

The center tester, black in color, is used as an ammeter and is in series in the six volt circuit (immediately at the ESC output). It detects the sum of the currents flowing in the esc/motor circuit plus the small current flowing in the coil.
Blue/black arrow and blue/red arrow of the two relay circuit.

The larger yellow tester on the right is used as an ammeter and is placed in series on the 12-volt battery circuit.

In the videos you can see that the remote control lever is gradually moved forward.
At the same time you can observe the gradual increase in voltage on the blue tester.
At the same time you can see the current rising on the black tester.
Instead, on the yellow tester the display shows 0 Amperes, a clear sign that the 12 volt circuit is open and therefore not active.

As soon as the voltage, measured on the blue tester, exceeds a certain threshold, we see that:
the 12 volt motor starts to turn much faster,
the blue tester directly indicates just under 12 volts,
the black tester shows a few milliamps (not zero) because it continues to detect only the current of the coil circuit (current no longer flows in the ESC circuit),
the yellow tester measures the absorption of the current passing through the 12 volt circuit.

I made more videos to show you how, as I added diodes, the voltage drop increased.
In this way you can see how the activation threshold of the coil goes from 3.61 volts in the first video to 4.29 in the last video.
I could have continued to increase the voltage drop up to the maximum threshold but I stopped because I believe that this way the concept is understood well.


In the last video you can see the reverse gear being activated.
The blue tester shows negative voltage.
The black tester shows a reverse current.
The twelve volt circuit which is only fast forward never engages (and thank goodness!)



ADVICE FOR POSSIBLE PRACTICAL IMPLEMENTATION OF THE CIRCUIT

Always use fuses.

Consider the currents at play.
In this case they did not exceed 2 amperes even at 12 volts but the motor axis was free. With a propeller in water things change, absorption increases.
Pay attention to how much current, especially the relays, must support.
If you want to cause the voltage drop in a different way, remember that at least one diode is useful to not energize the coil in both directions.
Imagine a backward march which, if done too quickly, can become a sudden and disastrous forward march.
If you use two relays, make sure they are identical and do some tests. A single realis guarantees the simultaneity of the commutation.
The blue tester (not really mine, buy your own, hahahahahah) will be used to calibrate the coil's intervention threshold correctly and to your liking.
Don't be scared by the tangle of cables I made.
Work well done on a breadboard requires little space.

Hi Doug, your anecdotes about modeling experiences are always very interesting. I really like reading them.

The photos you attached do not allow me to decipher the circuit and transfer it to paper.
A more trained eye than mine would have no difficulty.

If you have the diagram and the list of individual components, attach it if you want.
I try to solve problems on my own but if I find help I don't mind at all and one day (even if not now) it might be useful to me.
But I understand that many things (notes, drawings, diagrams) are difficult to find after so many years, so don't worry if you don't have them.

I am currently interested in a low battery warning circuit and automatic engagement of the reserve battery and an ESC for brushed motors.
In fact, manual voltage variators are not very difficult to make with a few LM317, LM2576, etc. etc. (besides the fact that they can be found ready-made on the market for two or three euros), but the ESC would be more satisfying.

For the Esc I temporarily left the matter pending; after John and Roy's very useful suggestions, I'm waiting to find a simpler circuit with easily accessible components.

Lastly, a great undertaking (but it's utopia for me at the moment) would be to increase the transmission power of toy radio controls.

One thing at a time, I don't have time to do much anyway.

Ingenious Alessandro👍
Reminds me of the overdrive gear I recall from driving cars like Jaguar MK2 and Humber in the late 60s early 70s. Great days.
Also reminds me of the early days of sailing my 1/72 H Class destroyer, some 37 years ago.
She was fitted with twin 540 motors and a robust Hitec ESC with relay reversing and big ol' T03 type power transistor on the top of an alu box.
I fitted two 6V SLA batteries. Normal cruising at scale speeds on 6V.
Just for fun I fitted a relay to switch the second battery in series so I could make the guys with plastic RTR so called 'speed boats' look damn silly.😁
But I had the luxury of a spare channel to use to switch the relay.
Thus I could switch the ESC input from 6V to 12V and retain speed control.

Yours is a perfect example of making the most of limited on-board resources.
Chapeau mon ami👍
Cheers, Doug😎
Pics show a later 4 channel circuit board, using the same relay control principle of pulse position switching, which I used for switching four special functions. NAV lights, signal lamp (Aldis), smoke, Whoop whoop horn.
CD4001 ICs were used as pulse position detectors, with the switching position adjusted by the trim pots. Thus providing four functions from one TX proportional channel.😊

Greetings to all modelers.

Attention, we are not talking about the "Merchant of Venice" but it could make "Much Ado".
"but not About Nothing", those who want to take a nap and not be disturbed by the chatter should not waste time reading further.
Hahahaha, I'm joking of course.

More than 10 years ago, I built an rc model for my son (sooner or later I should put it in the "harbour" section of this site, I think it might be of interest to someone).
In a period of maximum economic savings I bought a radio control with only two channels (not on the internet but in the shop), an ESC for 8 euros and an even cheaper rudder servo.
The engine had instead been given to me previously.
An exceptional 24 volt brushed motor.

Since the sails I put on were just for beauty, two channels were enough for me (engine forward and aft, rudder right and left).

Realistic navigation for this type of vessel was achievable with 6 volt voltage and the stick in the middle of the way.
So I could have been satisfied with this configuration.

Yet I was always curious to see how it would perform under higher voltages.
Being a "displacement" and not a "planing" hull, its speed limit was still limited by the length on the waterline; however the effects would have been entertaining if not realistic.

I decided to try it at least at 12 volts, but with only two channels I didn't know what to do.
Another available channel would have allowed me to control a mechanical switch to be operated with another servo.
I didn't opt for a rheostat-based voltage regulator for many reasons.
The ESC I bought could handle up to 8 volts maximum so I couldn't connect the 12 volt battery directly.
How to do?

In the end I succeeded with a few electronic components recovered from electronic boards that people throw away.
You have no idea how many new and perfectly functional electronic components are thrown away (relays, transistors of all types, resistors, capacitors, coils, motors, etc., etc.)

The ship sails regularly using the 6 volt battery.
In this phase it is also possible to go in reverse and the radio control lever regulates the speed, increasing or decreasing it.
However, if a certain threshold is exceeded (switch all the way up or almost all the way up) the motor takes power directly from the 12 volt battery and no longer from the 6 volt one.
You can't reverse on 12 volts. Only forward, or we return to 6 volts.
Furthermore, at 12 volts you cannot adjust the speed because the battery connects directly to the motor.

The only drawback is that the transition from 6 to 12 is sudden, I'm looking for a way to make it as gradual as possible. I have an idea but I have yet to test it.

A few days ago I took out all the old wiring of this circuit I described; I had left them inside the ship even though they were now unused. Out of laziness I had never taken them off.
I tried to reconstruct a pattern by looking at the connections I had made. But, even though I had done it myself, I got impatient with untangling that tangle of cables and decided to do it all over again, trying to remember the reasoning I had done.

In the end I arrived at this simple and intuitive system that I attach.

The first is a generic scheme while the second relates to the specific use of two relays (with 6 volt coil).
It is better to use the contacts operated by the same coil (you are sure of simultaneity) but I have adapted to the circumstances.

It works fine, but I may have made some typing errors.

In my opinion, it also works for switching from 12 to 18 volts where the ESC can only support 12 volts. Logically the relays must be changed.

If any of you know other systems that are not mere mechanical switching (for example a winch that acts on the rotary knob of a voltage variator) I would be happy to know them.

In the next message I will explain how this simple scheme works for those who are interested and don't know.
I don't want to load too much information into a single message which then becomes difficult to read.
I hope this may interest you.