Can somebody please help me figure out the mechanics for my design project? (Need help with polarity

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#1 21682053 03 Mar 2019 10:16

Leo Freese Leo Freese

Anonymous

Post #1
21682053 03 Mar 2019 10:16

Hello I am re-designing a battery powered screwdriver and I need help figuring out how polarity switches work. I was going to use a 3 position DPDT slide switch to control the direction of the dc motor, but I don’t want the motor to start spinning as soon as I slide the switch to an on position. I want to switch it to the right or left, and then use a separate button to turn the motor on and off. Is there a way to do this using a DPDT switch or should I use something else instead? I am a beginner so any help is appreciated!I have attached an image of the DPDT switch and rocker that I was looking at.
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#2 21682054 03 Mar 2019 13:11

Chip Fryer Chip Fryer

Anonymous

Post #2
21682054 03 Mar 2019 13:11

HiIt depends on the screwdriver. If it is just a simple motor running through a gearbox then your approach would be fine and would do as you need as long as the switches are rated for the full load current of the motor, and from your post I suspect this is the case. However if the motor is being controlled by electronics (speed control) then this approach would either need to be modified or rethought.Regards
#3 21682055 03 Mar 2019 17:08

Leo Freese Leo Freese

Anonymous

Post #3
21682055 03 Mar 2019 17:08

Thanks for the feedback! It is just a simple 6v DC motor with a gearbox, but I don’t know what the full load current is. One of the DPDT switches says “6A/125V 3A/250V AC” and the other DPDT switch says “250V/16A 125V/16A AC”. Do you know if either of these would typically work with a 6V DC motor? And if so, which one should I use? Thanks again for the help!
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#4 21682056 03 Mar 2019 17:33

Chip Fryer Chip Fryer

Anonymous

Post #4
21682056 03 Mar 2019 17:33

HiAny of these would most likely be suitable as it is unlikely that with a six volt battery supply you will pull more than a couple of amps (briefly). If you have a multimeter it will be able to provide current (Amps) readings but I doubt if these switches would be troubled. All things being equal use the one that gives the best fit for your needs.Regards
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#5 21682057 04 Mar 2019 00:20

Leo Freese Leo Freese

Anonymous

Post #5
21682057 04 Mar 2019 00:20

Thank you Chip! One last thing... how would I make it so that the motor doesn’t move when I slide the DPDT switch, so that I can controll it with an on/off button?Does this just have to do with the way I wire it?
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#6 21682058 04 Mar 2019 00:31

Chip Fryer Chip Fryer

Anonymous

Post #6
21682058 04 Mar 2019 00:31

HiIf you go from the battery to the on/off switch first, then go to the DPDT before reaching the motor, you can then change the position of the DPDT whilst the motor is off.Hope this helps.
Regards
#7 21682059 04 Mar 2019 00:45

Leo Freese Leo Freese

Anonymous

Post #7
21682059 04 Mar 2019 00:45

Very helpful, thank you so much!
#8 21682060 04 Mar 2019 01:48

David Ashton David Ashton

Anonymous

Post #8
21682060 04 Mar 2019 01:48

Leo as above you don't need a centre-off switch as you will only use it to change from forward to reverse, the on/off is done by your button. I may be oversimplifying here but I thought a diagram might be helpful:
- put the on button before the speed control so the speed control won't drain the battery when the drill is off- I don't know what type of speed control you are using so just put that as a box- the DPDT Fwd/Rev switch is shown in the forward position, the horizontal lines will move to the other side to reverse. As shown you connect opposite sides of the switch to control the polarity of the voltage to the motor (The "X" connections in the middle of the switch)Cheers // David
#9 21682061 04 Mar 2019 02:26

Chip Fryer Chip Fryer

Anonymous

Post #9
21682061 04 Mar 2019 02:26

I need to learn how to attach and embed diagrams properly...
#10 21682062 04 Mar 2019 06:05

David Ashton David Ashton

Anonymous

Post #10
21682062 04 Mar 2019 06:05

@Chip...You need to save your diagram as a file on your hard disk, you can't paste them.Then click the little page with an arrow icon on the extreme right of the toolbarSelect your file and click confirm.I seem to remember the file cannot be too big, but otherwise it's quite easy. The only problem is it seem to be the luck of the draw how big it comes out. Wider diagrams seem to work better than small ones - the one above came out ok.
#11 21682063 06 Mar 2020 13:30

Angela Angie Angela Angie

Anonymous

Post #11
21682063 06 Mar 2020 13:30

Thanks for sharing this, For more information please click here.....https://www.klantenservicenummer.co/gmail-nederland/
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Topic summary

The discussion addresses controlling the direction and power of a 6V DC motor in a battery-powered screwdriver redesign. The user plans to use a 3-position DPDT slide switch to reverse motor polarity for direction control but wants the motor to remain off when switching direction, using a separate on/off button to start and stop the motor. It is confirmed that for a simple motor with gearbox, this approach is feasible if the DPDT switch is rated for the motor's load current. Typical DPDT switches rated at 6A/125V or 16A/250V AC are likely suitable for a 6V DC motor drawing a few amps. The recommended wiring method is to place the on/off switch between the battery and the DPDT polarity switch, ensuring the motor does not run when changing direction. The DPDT switch reverses polarity by swapping connections, and the on/off button controls power flow. A center-off position on the DPDT switch is unnecessary since the on/off function is handled separately. Additional advice includes placing the on/off switch before any speed control circuitry to prevent battery drain when off. Diagram sharing tips for illustrating wiring were also discussed.
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Can somebody please help me figure out the mechanics for my design project? (Need help with polarity

Didn't find an answer? Ask Artificial Intelligence

Topic summary