# Help Needed for Micro Switches Wiring Schematic

#### george0039

Joined Oct 15, 2008
167
Hello

I have started to build this 60cc syringe ballast tank for a remote control submarine project. The video link shows the 60cc syringe with 4 micro switches, one on each end of the syringe- Start and Finish Positions and 2 micro switches operated by a servo in the middle.

I need help because I can not see clearly what wire goes to what terminal of each micro switch. Can anyone draw with labels what the wiring is from the video link I, hopefully included for you to see. Computers are still new to me.

The wiring picture starts at 11:36 into the video and you can see the operation of it till the end. 13:09.

If you can help me with the connections, Thank You.

If there is a way to even simplify the wiring, let me know. Basically as is in the video and Extra - simpler way for wiring.
George
RC submarine Piston Ballast (Types of M4 Thread rod in syringes to save space)

#### djsfantasi

Joined Apr 11, 2010
6,838
Rather than show you how to wire the micro switches, I’m going to try and explain how they work so you can figure it out on your own.

Typical microswitches has three terminals, a lever (optional) and a button.

Most micro switches are very similar to a single pole, double throw switch. Otherwise known as a SPDT switch.

One terminal is labeled Common or Com. This terminal is what is switched between one of two terminals.

Another terminal is labeled normally closed or NC. This terminal is connected to common normally. I.e., if the ‘button’ isn’t pressed.

The third terminal is labeled normally opened or NO. This switch is NOT connected to the common terminal unless the ‘button’ is pressed.

#### jpanhalt

Joined Jan 18, 2008
10,260
That seems like an awfully complicated way to make a Harvard (aka programmable syringe) pump. The producer seems to be infatuated with his/her machining ability. Just count revolutions of the screw.

#### george0039

Joined Oct 15, 2008
167
I think this version is meant to be continuously controllable. since you control the servo and the motor works as long as you hold the control stick in that position. That is needed for submarine radio control.

#### jpanhalt

Joined Jan 18, 2008
10,260
If it is a servo motor, why do you need limit switches?

Tell us what you want to do, not how you think you should do it.

#### george0039

Joined Oct 15, 2008
167
O.K then. Please have a look at the video link included. That is what I want to copy. ALL I need is a schematic drawing showing what is shown in the video at 11:36 till the end. I need to see what aire connects to what Micro switch terminal and battery terminal. I JUST cant see it clearly enough in the video EVEN when paused. I want mine to work just like in the video.

THEN if there is a easier way to wire it up, I would like to see that version as an extra option.

IT has to be radio servo controlled to fill partially or full and empty partially or completely.

Thanks
George

#### jpanhalt

Joined Jan 18, 2008
10,260
As a general rule, I find it silly to repeat anything on "You Tube." Why would any reasonable person spend so much time making shaft couplings out of brass? Do you have that machinery? Do you know how to drill and tap two holes on center in a round tube? Buy them out of steel and get on with your real purpose. That was a worthless YouTube (as are most).

What do you want to accomplish?

#### george0039

Joined Oct 15, 2008
167
I refer to Post 6 above. The unit works without issue and others use the same method.
I know how to do the mechanical side of it. The wiring is ALL I am after.

#### djsfantasi

Joined Apr 11, 2010
6,838
If you know how to build the mechanical side, why would you put all of your hard work at risk for a diagram that you don’t understand?

#### Bernard

Joined Aug 7, 2008
5,656
Seems that we need much more information, pressure sensor, angle sensor, etc. I presume that
the syringe switches are for over travel protection. Just a drawing to illustrate a possible wiring
scheme. If the servo switches SW D, the syringe starts to fill, sub dives. If the syringe is full , limit SW opens & motor stops.
Servo is reversed, motor reverses draining syringe.

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#### george0039

Joined Oct 15, 2008
167
Hello Bernard
You pretty much have gotten what I am after BUT there is No pressure sensor, angle sensor etc.
In the video from the link I included in my first post. There are 2 micro switches on the syringe. one on the full side and one on the empty side. There are 2 more micro switches that a servo activates. One causes the geared motor to fill and the opposite one causes the motor to move the plunger to empty.
Besides the mechanical, which I understand. I JUST could NOT see clearly enough from the paused video what wire is connected to what point of each micro switch.

#### LesJones

Joined Jan 8, 2017
2,698
This is my interpretation of the wiring and an alternative way that may be better if the motor / limit switch part is a long way from the servo / micro switch part. In the original there would be five wires between the two parts. In the alternative there would only be two wires. The disadvantage is that it requires the addition of two diodes.

If you are not familiar with the abbreviations used on switch contacts then C stands for common, NO stands for normally open & NC stands for normally closed. I have just noticed that I have shown the C and NC contacts on the limit switches swapped over from the way they were connected in the video but it is functionally the same. (I.E The connection is broken when the switch is actuated.) If you decide to use the alternative circuit then I suggest building it without the diodes soldered to the switches. First fix one of the direction switches in the closed position and with the syringe about mid position power it up. Then actuate the limit switch that it moving away from. The motor will stop. Then connect a diode cross the contacts of the limit switch that you have actuated. If the motor starts then that is the correct polarity for the diode. If not reverse the ends of the diode. The second diode goes across the other limit switch so the diodes are either catode to cathode or anode to anode.

Les.

#### MisterBill2

Joined Jan 23, 2018
7,040
I watched that video and indeed it seems that there is mostly showing off of machining ability and resources. And there is no similarity to servo control, since the whole thing is operated by two switches activated by a rotary RC servo. If the ultimate goal is actually to control Mballast tank filling in an RC submarine then there are better ways. Far better than microswitches would be magnet operated reed switches. And if the only need is to stop the drive at the end of the stroke then just a simple current limiter will be adequate, along with a shaft stop to avoid jamming the piston against an end.
One more thing is that if the TS does not understand even such very fundamental circuits then it is not likely that the project will ever work. A simple motor control circuit is just not that difficult.

#### george0039

Joined Oct 15, 2008
167
This is my interpretation of the wiring and an alternative way that may be better if the motor / limit switch part is a long way from the servo / micro switch part. In the original there would be five wires between the two parts. In the alternative there would only be two wires. The disadvantage is that it requires the addition of two diodes.
View attachment 202335

If you are not familiar with the abbreviations used on switch contacts then C stands for common, NO stands for normally open & NC stands for normally closed. I have just noticed that I have shown the C and NC contacts on the limit switches swapped over from the way they were connected in the video but it is functionally the same. (I.E The connection is broken when the switch is actuated.) If you decide to use the alternative circuit then I suggest building it without the diodes soldered to the switches. First fix one of the direction switches in the closed position and with the syringe about mid position power it up. Then actuate the limit switch that it moving away from. The motor will stop. Then connect a diode cross the contacts of the limit switch that you have actuated. If the motor starts then that is the correct polarity for the diode. If not reverse the ends of the diode. The second diode goes across the other limit switch so the diodes are either catode to cathode or anode to anode.

Les.
Hi Les
Thank You for your reply and the 2 circuits. The diodes you suggest, can I use 4007 diodes?

If as mentioned below there are other ways to run a remote controllable ballast tank then please go ahead and let me know. Just note that the ballast tank has to be controllable by the operator through the transmitter.

George

#### george0039

Joined Oct 15, 2008
167
I watched that video and indeed it seems that there is mostly showing off of machining ability and resources. And there is no similarity to servo control, since the whole thing is operated by two switches activated by a rotary RC servo. If the ultimate goal is actually to control Mballast tank filling in an RC submarine then there are better ways. Far better than microswitches would be magnet operated reed switches. And if the only need is to stop the drive at the end of the stroke then just a simple current limiter will be adequate, along with a shaft stop to avoid jamming the piston against an end.
One more thing is that if the TS does not understand even such very fundamental circuits then it is not likely that the project will ever work. A simple motor control circuit is just not that difficult.
Hello
Thanks for your reply. If you could include some circuits for me to see, that would be great. The circuits have to be able to control the ballast tank not just fully but partially, full or full/empty by radio control.
Thanks
George

#### djsfantasi

Joined Apr 11, 2010
6,838
Just wanted to add a quick not to clarify that I misunderstood your question. That happens. But I’m glad that you’re getting help.

#### LesJones

Joined Jan 8, 2017
2,698
Hi George,
1N4007 should be fine (Or any of the 1N400x series diodes as the voltage is so low.) as looking at the video it looks like the motor as small ad probably takes less than 1 amp. The limit switches need to be normally closed so I think finding normally closed reed switches might be difficult. Reed switches and magnets would not give positioning as accurately as micro switches. I have used normally open reed switches as limit switches by connecting them between the base and emitter of a transistor that was biased on via a resistor connected to the base. I did think of suggesting using a circuit that detected the pulse width of the signal that drives the servo and using it's output to drive the motor using an H bridge (Or relays.) but I thought that would be too complex for you and would probably take up as much space as the servo operating the micro switches. If the radio control system had two spare on/off channels you could use these to drive relays or an H bridge that would control the motor.

Les.

#### george0039

Joined Oct 15, 2008
167
Hi Les
I also forgot to say that free space is VERY limited so I think the above approach is a go for now.In R.C submarine work people follow the KISS principle in there projects. Its also easier to diagnose a problem and fix it.
Thanks Again for the help.
Time to collect parts and try out the circuit.
George

#### MisterBill2

Joined Jan 23, 2018
7,040
Hi Les
Thank You for your reply and the 2 circuits. The diodes you suggest, can I use 4007 diodes?

If as mentioned below there are other ways to run a remote controllable ballast tank then please go ahead and let me know. Just note that the ballast tank has to be controllable by the operator through the transmitter.

George
For the low voltages involved you could use 1N4001 diodes, rated at 50 volts . Or any of that series of 1 amp diodes.
For a lower friction ballast tank you could also use an arrangement similar to a bladder type hydraulic accumulator,which has only the rolling friction of the bladder, and no moving seal. The bladder material could be something like thin-wall silicone or urethane tubing, moving inside a rigid plastic tube. An added advantage is that you would not be restricted to only the size and volume of syringes. And with no sliding seal the friction would be less. It may even be possible to use a plastic ot metal bellows for even less friction yet.

#### Bernard

Joined Aug 7, 2008
5,656
The diodes in post # 12 need to carry full motor current, 1N4007 I believe are rated @ 1 A. I would prefer shottky diodes with lower V drop.