Large Scale Central

Wiring diagram for dpdt switch & motor?

Electronics
#1

I’m trying to figure out the correct wiring diagram to use a double pole, double throw switch with a charging plug. I’m trying to do this with out a dpdt center off switch. I have a 9 volt battery, and a small motor that I’m trying to reverse/forward. The battery needs a charging jack as it will be sealed up. I’m not sure where to put the charging jack into this circuit.

I will also be adding a push button on/off switch. Granted it would be easier to have a dpdt center off switch, but I don’t have one handy.

Craig

#2

Craig Townsend said:

I’m trying to figure out the correct wiring diagram to use a double pole, double throw switch with a charging plug. I’m trying to do this with out a dpdt center off switch. I have a 9 volt battery, and a small motor that I’m trying to reverse/forward. The battery needs a charging jack as it will be sealed up. I’m not sure where to put the charging jack into this circuit.

I will also be adding a push button on/off switch. Granted it would be easier to have a dpdt center off switch, but I don’t have one handy.

Craig

What I did was make one side of my DPDT switch the on/off switch and the other side the charging plug, so when the loco was off the charge plug was still live across the battery.

As there is no load across the plug (it is an open circuit) no current is drawn. I used a recessed plug to reduce the risk of shorting out the battery.

I tried to add a wiring diagram in a Word doc that I have but the site does not like it it only wants pictures evidently.

#3

Craig

Sounds like you want to wire a DPDT switch for FWD-REV together with a charging socket. You could use a charging SPDT plug/socket similar to what Airwire utilizes to isolate the battery while under charge and as an ON/OFF switch too. I used a charging socket on my Mogul as described years ago works great. The socket is wired to provide a N.C. (closed circuit) between the battery and motor under ON conditions. Under charge the N.C. circuit is opened when the plug is inserted, isolating the motor from power and providing a path to the battery for charging by closing the N.O. circuit of the socket. You’ll need one DPDT switch and one SPDT charge socket and two male plug ends. One plug end is wired to the chargers output leads for charging and the second plug is used loose (no wires), insert loose plug into charge socket and the socket doubles as an ON/OFF switch. One caveat herein is the current handling rating of the charge socket, low current demands only IMO.

Michael

#4

Michael,

Yes I think I understand what your saying, and how it would work. I’m pretty confident that my motor is pretty low current 700 ma at full stall. Old Lego motor. I think something along the lines of a plug as a switch should work.

The bigger question is, sourcing a rechargeable 9 volt battery and charger. Amazon has 2 packs with a charger.

#5

#6

Craig

I’d suggest no problem with the Lego motor… I have a LGB Mogul set-up with a 6 cell 22V, 2200mAh Li-Ion battery with an original wireless QSI G-wire Receiver and Magnum sound decoder, pretty sure I’m drawing around 1 amp with my setup.

Eric

No provisions for FWD-REV DPDT operation.

Michael

#7

For those interested this is where I’m getting the power information.

"Electric Technic Motor 9V

Lugnet Partsref 2838c01, Peeron 2838c01, Lego 74569

The older 9V Technic motor (1990). Ungeared, it has a high rotation speed and low torque, so for most applications it requires an external gear reduction."

http://www.philohome.com/motors/motorcomp.htm

9v supply gets you:

4100 RPM (yes I have a gear reduction)

No load current 35 mA

Stalled

Torque .85 N.cm

Stall Current 700 mA

|


2838

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Torque

|

Rotation
speed

|

Current

|

Mechanical
power

|

Electrical
power

|

Efficiency

|
| - | - | - | - | - | - | - |
|

6 V

|

0.45 N.cm

|

580 rpm

|

0.32 A

|

0.27 W

|

1.9 W

|

14 %

|
|

7 V

|

0.45 N.cm

|

1000 rpm

|

0.32 A

|

0.46 W

|

2.3 W

|

20 %

|
|

9 V

|

0.45 N.cm

|

2000 rpm

|

0.32 A

|

0.9 W

|

3 W

|

31 %

|
|

12 V

|

0.45 N.cm

|

3300 rpm

|

0.33 A

|

1.5 W

|

4 W

|

39 %

|

#8

Missed the reverse direction requirement (thanks, Michael). Provided you don’t mind having the charge jack connected to the battery full time, this would work for your single SPDP and additional SPST.

#9

Craigs’ DPDT center off will work without the additional SPST if he always remembers to have the DPDT in the off position when charging.

#10

Paul,

I don’t have a center off switch on hand. If I end up having to order parts, I will toss in a dp dt center off switch. So for now, it’s two different switches. The other limiting factor is the room inside. The space I have barely fits the 9 volt battery, so I have to get creative on switch size and location. I’m also trying to hide the switch in plain sight.

#11

Craig Townsend said:

Paul,

I don’t have a center off switch on hand. If I end up having to order parts, I will toss in a dp dt center off switch. So for now, it’s two different switches. The other limiting factor is the room inside. The space I have barely fits the 9 volt battery, so I have to get creative on switch size and location. I’m also trying to hide the switch in plain sight.

You could copy Newquida and have the on/Off switch covered with a toolbox or considering its such a low current a reed switch under a metal plate with a magnet disguised as a piece of equipment to activate it.

I have actually seen the reed switch and magnet idea used as a FWD/REV switch just depended which side of the loco the magnet was placed bit of creative wiring but it is in plain sight.

The pics attached show how I did a small loco with on/charge on one side and direction on the other way out in plain sight.

#12

The plan right now is to hide the fwd/rev switch as part of the external engine carburetor. Move it forward/back and corresponding direction.

I have some reed switches with large magnets that I could also try for an on/off switch. The problem with that idea is that I could use the same “hiding” spot for the charging jack and wire it as Michael suggested above.

#13

This is how I wired my Mogul multi-tasking the charge jack as an ON/OFF switch and a charging jack… I used a fuse that’s not depicted in the attached drawing.

Is there a current sticky on posting pictures? I looked didn’t find anything that seemed to be current. I was able to attach the thumbnail below, I’d like to post the full size - constrained photo.

Michael