There is a more complex design, I posted in this https://forum.allaboutcircuits.com/...house-roof-window-control.134958/post-1131056 thread.
You should stop the motor briefly before changing direction.
There is a more complex design, I posted in this https://forum.allaboutcircuits.com/...house-roof-window-control.134958/post-1131056 thread.
You should stop the motor briefly before changing direction.
The motor stops as soon as I lift off the momentary switch and the internal spring returns it to center OFF. I don't think I could press in the other direction fast enough NOT to stop the motor.You should stop the motor briefly before changing direction.
Hi Les, Yes, the motor must be a permanent magnet because the motor definitely reverses when the rocker switchjkbrand, Are you SURE that the motor is a permanent magnet motor ? (NOT a shunt wound or series wound motor.)
Only permanent magnet motors reverse with reversing the supply polarity.
Les
You know, early on I had the same thought about the potential for diodes to limit direction of flow. Where can I learn more about determining a "properly rated diode"? The motor is small, and at startup, seems to draw no more than .3 amps at 5V as shown by the display on my 10amp DC power supply. In fact, it's so small the leads on the motor are around 22 or 24 gauge.Make sure the motor reverses when changing the polarity.
What you can do is: Use diodes in parallel with the limit switches. The limit switches would be in series with the motor.
1. You have the switch open the circuit when it reaches limit A, then insert a diode so current can flow opposite limit A.
2. Do the same for limit B.
Without the diodes, the motor would just stop when they hit the limit switch and you would not be able to move it in the other direction.
I won't draw the circuit. Just put the limit switches in, activate one. Put the switch in the opposite direction, the motor won;t move. Insert the properly rated diode in the direction that causes the motor to move away from the limit switch. Both limit switches would be closed when movement can occur in both directions.
In your circuit, the limit switch MUST handle the motor and start-up current and wont stop instantly,
For a visual. Your switch gets the customary X wiring.I need help visualizing where in my circuit the proper diodes should go
Below is a photo of the limit switch I'm using, and a photo of my connection to the switch.Here is the annotated DPDT switch. Pix of limit switch(es) will follow after I get out to my wood-working shop.View attachment 238003
Thanks, KISS--You say "Your switch gets the customary X wiring." I really am ignorant in this arena, but I'm trying to learn. I am aware that a diode is polarized and it will allow current to flow in one direction and not in the other. That is the extent of my knowledge of diodes. What is 'customary X wiring' to a lay person? I ask because I think the answer might explain somethingFor a visual. Your switch gets the customary X wiring.
For visualization, take each of the motor leads and put a normally closed limit switch there,
You will be putting a diode across each switch. The diode conducts when the arrow is + and the band is negative, Conventional current (+ to -) follows the arrow. One diode will be facing the motor and the other will be facing away from the motor.
Test one limit switch at a time. Move motor. Activate. Reverse direction. Add diode in the direction that allows the motor to move. Do, the other one.
Look at step 3, here: https://www.instructables.com/HOW-TO:-Wire-a-DPDT-rocker-switch-for-reversing-po/"Your switch gets the customary X wiring."
While this proposed scheme could probably be made to function, it is vastly more complex than the application requires. It is the exact opposite of the directive "Keep It Simple, Sir."Look at step 3, here: https://www.instructables.com/HOW-TO:-Wire-a-DPDT-rocker-switch-for-reversing-po/
The switch has the typical "X" pattern for a polarity reversal switch.
I'm not too crazy about the DC switch rating (0.3A) and the motor. The good part is that it would be mostly used for interrupting current and not switching current. When an inductive load starts up, the system basically sees the wire resistance for a short time. There is this little rule that says the "current through an inductor cannot change instantaneously"
The construction of a switch does depend on whether AC or DC is used. You actually could have different make and interrupting ratings. For very low current applications there is a "wetting current" specification or the minimum current you should switch. Switches the work with logic thus have precious metal plating.
Take a typical ceiling fan which has a slide switch to reverse polarity. The switch will last a long time if you turn off the motor first before switching.
For now, not sure how to add limit switches, but this https://www.canakit.com/Media/Manuals/UK1122.pdf MIGHT be good choice. You might need some "glue logic" to make the limit switches work and also brake the motor. "glue logic" is a term for a small circuit designed to change the behavior of another or interface to it.
You would have the logic inputs of:
Direction
Enable
Limit switch A
Limit switch B
and outputs of
Direction and Enable
You can "cheat" and use two 74150 Ic's e.g. https://www.jameco.com/shop/ProductDisplay?catalogId=10001&langId=-1&storeId=10001&productId=49509
The inputs would have pull up resistors or pull down resistors. TTL does float high when an input is disconnected.
A pull-up could be like a 1K resistor. Pull up means connected to +5, pull down gnd.
You assign the inputs A, B, C and D and one 74150 would control direction and the other enable.
You can easily make any truth table you want by connecting what you want. e.g. if D, C, B and A are all low, the output (W) is NOT E0. or the reverse of what E0 is tied too (GND or +5).
Just for reference, the enable input is usually pulse width modulated which controls speed.
Your DPDT switch would control direction and enable. One pole would be direction and the other enable.
With TTL, you would generally want enable to be not enable so if the switch is disconnected, the motor stops.
We have no idea the application or how reliable this thing has to be. Breadboarding two IC's, two ceramic capacitors and 4 resistors might be over your head.
I'd probably use a SIP header and a shunt. e.g. 3 rows of 16. https://www.peconnectors.com/pin-headers-straight-1x-row-.100/hws16317/ and these: https://www.peconnectors.com/index.php?p=catalog&mode=search&search_str=shunt
The middle row is the not E? pins, the ends GND and +5. You just move the shunts to a 1 or 0 until you get it right.
This could be "way over your head"?
The advantage of speed control is torque remains constant. 100% could be full speed or 100% could be off.
PWM boards are available on ebay too.
We don't even know the application, so you can't make that statement.While this proposed scheme could probably be made to function, it is vastly more complex than the application requires.
Here is a picture of my motor. It is small with an integrated gear box.Once again, the circuit as posted works. trace the current path through either direction. THE diode scheme is OK for when both switches are in series with the motor. That is a very different scheme. But if this is a 2 amp motor then the 1N400x diodes are only one amp and they will fail. And if the diodes can't be near the motor then the wires get complicated.
So now another question: can we see a picture of the motor as it is? Ie it jusst a motor or is there some additional hardware associated with it?
I will try to take a pic of the wiring tomorrow when I get back home. In the meantime, I can confirm that pressing end "A" stops the motor. Pressing end "B" as I recall also stops the motor. Same, I think, with the other limit switch, but let me check tomorrow to be sure. Thanks for weighing in.Can you post a picture so that we can follow the wires to check THAT IT IS WIRED as shown in your diagram. I agree with the others that it should work if wired as in the diagram.
Can you confirm that if it is traveling towards end "A" that pressing end "A" micro switch stops the motor and that pressing end "B" micro switch does NOT stop the motor.
Can you confirm that if it is traveling towards end "B" that pressing end "B" micro switch stops the motor and that pressing end "A" micro switch does NOT stop the motor.
I was basing my suggestion of 1N400x series diodes on your current reading of 0.3 amps in post #26
Les.