# Help Need a Circuit for a Micro Timer Motor control

#### george0039

Joined Oct 15, 2008
167
Hello

I need a Run Timer Circuit for a motor control. The only battery is the main battery; 3.7v, 200mAh Lipo, 1-2A N40 D.C brushed motor.
I need the circuit to be able to fit inside a tube with 10mm Inside diameter.
I would like a run time of 10 seconds. I have lots of 555, could it be done parts soldered to the 555 leads with no crt. board?
It would have a reed switch with an external magnate, remove the magnet, R.S closes, timer is on, motor runs for 10 sec. To reset it, add magnet again and then repeat start.

Can anyone help with a Basic NON programmable circuit? Why Non programmable, well I have Not had any programmable I.C experience and I have LOTS of old I.Cs, thought I might try to recycle, IF possible.

Thanks in advance for the help.
George

Well I think I should include, can this be done / made with a programmable chip and circuit to fit the above listed needs?
If so, can you show the circuit and give details please.

Thanks

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#### george0039

Joined Oct 15, 2008
167
Hello again

I could really use help with this circuit wish. I have the tubing that will hold it already 3D printed and waiting for this circuit.

Please let me know if anyone can help me with this.

Thanks
George

#### Sensacell

Joined Jun 19, 2012
2,931
Maybe you will get more bites if you provide more information about what this is and how it's supposed to work?
How accurate and repeatable does the 10 second period need to be?

#### Alec_t

Joined Sep 17, 2013
12,466
Googling '555 monostable circuit' should give you lots of hits.
How long is the tubular space for the circuit?
Do you have the through-hole or surface-mount version of the 555?
Is it a CMOS 555 or a bipolar type?

#### AnalogKid

Joined Aug 1, 2013
9,628
Because of the 2 A load you will need a power transistor to drive the motor, something like a small power MOSFET for best efficiency. A TO-220 package is very common and cheap, but it is slightly over 10 mm wide. A 555 circuit with the reed switch connected to the Reset input will do the timing.

1 - 555
1 - R (timing)
1 - C ( timing)
1 - C (decoupling)
1 - FET

ak

#### KMoffett

Joined Dec 19, 2007
2,918
Because of the 2 A load you will need a power transistor to drive the motor, something like a small power MOSFET for best efficiency. A TO-220 package is very common and cheap, but it is slightly over 10 mm wide. A 555 circuit with the reed switch connected to the Reset input will do the timing.

1 - 555
1 - R (timing)
1 - C ( timing)
1 - C (decoupling)
1 - FET

ak
I wonder if anyone has ground down the edges of a T0-220 to make it fit in a narrow space.

#### AnalogKid

Joined Aug 1, 2013
9,628
I wonder if anyone has ground down the edges of a T0-220 to make it fit in a narrow space.
No reason why that wouldn't work, but there are other packages. On Semi and IR have power MOSFETs in 8 pin DIP, and all of the older SMT packages have gull wing leads that can be soldered to without frying the part. Look into TO-251, DPAK, and SOT-223.

ak

#### Bernard

Joined Aug 7, 2008
5,788
FDD6530A, N ch. FET, LL, SMT, 36 m ohm, 20 V, 21A, gate +-8V, starts conducting @ 1V, about 6 mm wide.
FZT849, NPN, SMT, 80V, 7A, B=100, 6 mm wide. I have both.
Maybe a 1 mm X 5 mm X 25 mm mounting strip, fiber glass-plastic or cardboard topped with strip of Cu foil as ground. Top of 555 cemented to strip for dead bug style wiring. Small ends of leads folded over but not touching each other. !0 uF , SMT 3 mm X 2.3 mm X 2.5 mm; .047 uF , SMT, about 1 mm X 2 mm X 1 mm.
4 Rs, 1/8 W, about 4 mm X 2 mm with .4 mm leads. Reed SW 21 mm X 2.55 mm. I have all but 555.

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#### george0039

Joined Oct 15, 2008
167
Hello again
Thank You to ALL who have replied.
Here is what I want this for. I am a remote control model boat builder. My R.C boat is a WWII Torpedo boat and I would like to have working electric torpedo on it.
Sorry BUT I can load pictures here as I dont know how to.

The torpedo body (tube) has been 3D printed to represent the scale of 1/32 of the real one.

Its inner diameter, I.D is 15.0mm MAX. I hope for a little smaller circuit due to internally having to adjust its location and weight is a factor as well. Have to keep total weight as low as possible.
As for its length,1" or 25mm Max. if shorter better.

Yes the Run time is important and I would like it to be 10 sec. every time. That way if it goes astray, it wont disappear.

Also Yes I have lots of NE555P 12AT68M & 7555 IPA V21225Y through hole I.Cs.

I hope someone has a working circuit that they would share.

PLEASE include ALL part I.Ds with a sample circuit.
Thanks
George

If these I.C won`t work then let me know what I need and I will get them.

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#### Bernard

Joined Aug 7, 2008
5,788
About 7years ago TS, trout , was building a 1;72 scale electric torpedo. No final report.

#### Bernard

Joined Aug 7, 2008
5,788
Do you have a form B , NC, reed switch? NO is more common. Either will work.

#### george0039

Joined Oct 15, 2008
167
I have the reed switch, motor, main battery.

#### AnalogKid

Joined Aug 1, 2013
9,628
When the magnet is *not* near the switch, is the switch open or closed?

ak

#### george0039

Joined Oct 15, 2008
167
closed and torpedo motor is working. When magnet is near, reed switch is open and motor is not working

#### Bernard

Joined Aug 7, 2008
5,788
'Tested this circuit on solderless breadboard. Time with pot. for R3 = 10 sec. Magnet on tube = motor off;
remove magnet motor on for 10 sec. C 1 about + - 10%. Replaced pot with 1 M , time 11 sec.
Woops:

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#### Bernard

Joined Aug 7, 2008
5,788
RE scan.

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#### george0039

Joined Oct 15, 2008
167
Hello Bernard

First, Thank You for your Time and Help.
Sorry I have to ask you this. I printed your circuit but it was upside down, no big deal. I just have some problems seeing the parts values clearly. Would you mind telling me if these are correct values?
Reed SW NC
R1 10kohm
R2 100k
C2 0.047uF/ v?
C1 ???/v?
U1 7555
C3 .1 uF/v?
C? 10??/v?
Transistor DGS ????????
Thanks again

#### Alec_t

Joined Sep 17, 2013
12,466
Add a freewheel diode across the motor?

#### Bernard

Joined Aug 7, 2008
5,788
V of all C's 16V or greater. C1,C4, 10 uF @ 25V. surface mount, SMT. You deciphered Rs correctly.
FET FDD6530A. I must run- getting stitches out. Appointment at 8:20, out the Dr office at 8:21.
A diode could replace C3. C2 any thing from .1 to .01 uF. I had .047 in SMT.
Reed sw form B, NC, I really used a form A, NO but reversed operation of magnet.

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#### AnalogKid

Joined Aug 1, 2013
9,628
I must run- getting stitches out.
Always better than getting them in.

ak