Total NOOB looking for help with motor direction.

[Ross1966]

Hi,

I am looking for help in building a circuit that will make my electric motor travel in a clockwise direction then after hitting a switch travel in a counter clockwise direction. Think of it like a teeter todder, when the teeter todder hits the ground on the one side the direction of the motor switches and the teeter todder is told to travel in the opposite direction. Can anyone help me out? I need to know if some thing already exists out there that I can just buy or if I need to build it? If I do need to build it what parts would I need? Any help is very much appreciated.

Ross1966

 

[Ross1966]

, Here is a link to Video that is similar to what I am trying to do. I will not be using the linkage to the motor like in the video, I will just be running the motor directly to the piece of wood. Again at the pivot point just like a teeter todder.

 

[crutschow]

You could use two limit switches, and a latching DPDT relay. The relay is wired as a bridge to reverse the voltage to the motor each time it is triggered by the corresponding limit switch. You will also need 4 diodes to protect the relay contacts from the motor inductive spike.
Does that sound okay to you?

What is the motor current and the power supply voltage to the motor?

 

[audioguru]

The video does not show a motor. Instead it shows a motor and a gearbox. The gearbox slows the speed and increases the torque.
The electronic circuit stops the motor for many seconds before the motor begins running in the opposite direction.

 

[Ross1966]

Here is a link to the motor that I have, I believe that it is low voltage 12v but it does not say what the torque is https://incubatorwarehouse.com/5rpm-dc-motor.html. Is this a relatively easy thing to build?

 

[Ross1966]

I do not need the gear box, That is why I specified that I would be connecting my motor to directly drive the wooden stick. I am needing info on making the circuit that will do what you described do you have any much needed advice on that?

The video does not show a motor. Instead it shows a motor and a gearbox. The gearbox slows the speed and increases the torque.
The electronic circuit stops the motor for many seconds before the motor begins running in the opposite direction.

The video was strictly for explanation purposes

 

[KeepItSimpleStupid]

The stock number suggests 1W, so probably none of the major precautions are necessary. i.e. stopping briefly at the end of travel or dynamic braking.

I found something strange yesterday https://www.airotronics.com/site/product-trueoff_TGMT.php A relay that delays on power OFF.

So, an impulse relay and one of the relays above would probably do it, but I'm afraid the cost would be too high. The limit switches would be wired with diodes, so when the limit occurred the motor would stop. The timer activated and the system would toggle the direction. I really don't like the idea.

A www.picaxe.com processor would do nicely with an H-bridge

 

[audioguru]

Your motor turns VERY slowly so of course it has gears. The one in the video turns half a turn in about 8 seconds so it turns at about 4 RPM. The motor in your link turns at 5 RPM so it is only a little faster.
Why are you turning a stick back and forth?

 

[Ross1966]

Why are you turning a stick back and forth?

The stick is connected to egg trays via a pushrod and the egg trays are slowly rocked back and forth with the eggs in them so the embryo does not sick to the shell.

 

[audioguru]

If the motor is connected directly to one long piece of wood then it loses some torque and might not be strong enough. The video uses three levers to gain some torque.

 

[4pyros]

Going back and forth is easy with limit switch's.
Do you want a timer too?

 

[aquamon]

Made a "RELAY"-less H-Bridge out of 5 NPN's...
What you think?

 

[audioguru]

Q2 is an emitter-follower with a voltage loss of maybe 1V when the motor current is low. R2 also causes a voltage loss at the motor.
If Q2 is a PNP transistor then it can properly switch completely on with a voltage loss of only 0.05V.

 

[alec_t]

Wouldn't it be simpler to use a crank mechanism so that you don't need to reverse the motor?

 

[aquamon]

Q2 is an emitter-follower with a voltage loss of maybe 1V when the motor current is low. R2 also causes a voltage loss at the motor.
If Q2 is a PNP transistor then it can properly switch completely on with a voltage loss of only 0.05V.

Well, it works and an "improvement" rather than "just saying" would be more helpful, wouldn't you say?
I also tried very hard to stay away from PNP's as this was a personal challenge to use the most commonly available parts (TIP 122/C945) just lying around.
Also, what is <1V loss comparing to PWM systems?

This was actually made to convert an RC helicopter to a boat (8.4v); using the LED Light "ON" switch (on remote) to activate reversing the dual motors (already a PWM system): 'cause a boat w/out reverse just isn't any fun.

I must say I love how it swings INSTANTANEOUSLY back into FORWARD!

Full Schematic uploaded; although diagram states 6V-12V, check ratings for high-end voltage limits...wonders w/ high current mods.

 

[aquamon]

Q2 is an emitter-follower with a voltage loss of maybe 1V when the motor current is low. R2 also causes a voltage loss at the motor.
If Q2 is a PNP transistor then it can properly switch completely on with a voltage loss of only 0.05V.

in other words, please post your improvements via diagram?
(Actually, the comment about R4 on the schematic was before rev1.1; is n/a).
Thank you!

 

[kinarfi]

I simulated your drawing and it looks like reverse is NOT modulated, if you don't need modulation in reverse, this works,

 

[Colin]

You can' drive 2N3055 with 39k

 

[audioguru]

Emitter-followers are not switches. They have too much voltage loss. They should be replaced by PNP transistors.
Darlington transistors also have too much voltage loss. They should be replaced by P-channel and N-channel Mosfets.

 

[Scotophor]

Wouldn't it be simpler to use a crank mechanism so that you don't need to reverse the motor?

I second this notion, crankshaft or cam action can give oscillating motion without reversing the motor. Also, you could probably get by with a lower gear reduction, say 1 RPM or less, which would give increased output torque.

Also, pay careful attention to the video... the gearmotor does NOT reverse direction each time it stops. It runs clockwise the first time it runs, then counter-clockwise each of the next three times. I suspect its a type of motor (induction motor?) that has no preference of which direction to turn, and will start moving in a random direction each time power is applied or will reverse itself if it is physically blocked. I once had a small AC-powered motor like that which came with an Erector set, and I currently have several even smaller ones that spin ornaments on my Christmas tree, and run by plugging in in place of a miniature light bulb (series-string type).