10 second runtime

Thread Starter

trout

Joined Dec 22, 2011
27
Bill and Bernard,
You guys are amazing!
I thank you for all your help on this. May this year be a prosperous and peaceful year!
I look forward to the first eTorpedo being built!
Peace,
Tom
 

Thread Starter

trout

Joined Dec 22, 2011
27
Bill, I originally in my head thought of capacitors as a way of doing this, but when I looked up capacitors - i tried doing the math- the size of the caps was huge! If you come up with an idea, I will get the parts and try it! Thank you again!
 

Wendy

Joined Mar 24, 2008
23,421
I'll draw a schematic if you don't mind, it may take a day or so. So many projects, and so little time. I would start building (or drawing using a POP (Pile of Parts)) as your guide. The electronics are going to be the small part.
 

tracecom

Joined Apr 16, 2010
3,944
Just for your reference, Nuts and Volts mag, December 2011, had an article about creating a very small power-on timer. They built it using a PIC10F200 microcontroller, one transistor, one diode, two caps, and two resistors - all SMD.

 

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Bernard

Joined Aug 7, 2008
5,784
There is an error on page 20 drawing, the connection between C3-R4-R5 does not go to ground- slip of pen. D1 does effectivly stop clock leaving pin 2 high holding motor off.
 

thatoneguy

Joined Feb 19, 2009
6,359
I'm curious, how do you plan on retrieving your torpedo(s)?

Unless you are running in a swimming pool, it should explode instead. :D

The SR66 battery you posted will be enough for about 1 shot, so it could also be the timer. You may need to experiment with run time with batteries that small.
 

Wendy

Joined Mar 24, 2008
23,421
A dime is around 0.7" wide, so I suspect that circuit is going to be too big. I think you have the right idea though.

Are you still aiming for under ¼"?

What size of capacitor would you need to duplicate a timer (I seem to remember you mentioning you had calculated it)?
 

tracecom

Joined Apr 16, 2010
3,944
A dime is around 0.7" wide, so I suspect that circuit is going to be too big. I think you have the right idea though.

Are you still aiming for under ¼"?

What size of capacitor would you need to duplicate a timer (I seem to remember you mentioning you had calculated it)?
I think you are responding to my post about the N&V article, but I am not the OP, so I don't know what his size limitations are. With regard to your question about capacitor size, I assume you are referring to a 555 circuit. In that case, the combinations of R1/C1 that (according to the formula) will work for 11 seconds are: 1 MegOhm/10 μF, 10 MegOhm/1 μF, 100 MegOhm/.1 μF. I don't have a 100 MegOhm resistor, so I haven't tried that combination. My assumption is that a .1 μF cap is preferred because of its smaller size.

If you are referring to the N&V article, their PIC10F200 timer uses a .1 μF ceramic and a 10 μF tantalum, both SMD.
 

Thread Starter

trout

Joined Dec 22, 2011
27
@Bill - Mind? No, I am thankful and can wait! I will build large scale to play with it then go small for pool testing.

@tracecom - Are you trying to scare me away? :) It is not working, but making me more determined.

@thatoneguy - Usually pool. No exploding torpedoes,but some use depth charges - http://www.youtube.com/watch?v=AFOFBqXIGUg&feature=related
I'll pass on that too!

Happy New Year to all!
 

tracecom

Joined Apr 16, 2010
3,944
@tracecom - Are you trying to scare me away? :) It is not working, but making me more determined.
Not at all. I admire your enthusiasm, and after seeing the N&V article, I am convinced that a timer can be built that will fit inside a 1/4 inch tube, but to put it on a PCB, it will have to be SMD. Maybe Bill can come up with something that doesn't require a PCB.
 

Wendy

Joined Mar 24, 2008
23,421
OK, but before you start on the electronics I would build a simple version that is on/off.

I think you will find the electronics relatively simple compared to the rest.

I have to admit I loved the reed switches, I've never seen those.
 

Bernard

Joined Aug 7, 2008
5,784
Samples of thin wall, .31 mm, 8.64 OD brass tubing, with ends sealed, sink like rocks; loaded with motor, battery & timing where will it go? Does motor really pull 900mA?
 

Audioguru

Joined Dec 20, 2007
11,248
The tail motor on a toy Air-Hogs Havoc helicopter is 6mm (it will fit into a 1/4" tube) in diameter by 12mm long. It operates from a 3.7V Li-Po rechargeable battery cell.
 

Thread Starter

trout

Joined Dec 22, 2011
27
Help me understand, lets say 3v motor, running 10 seconds, un-sure of amp needs say 1/2?
P = I V = (.5 amps) (3 volts) = 1.5 watts x 10 seconds =15 watts??? That is why I did not think capacitors would work. Even running the motor at 2v seems like a lot. Am I way off here? again please excuse my ignorance.
 

Wendy

Joined Mar 24, 2008
23,421
You may find caps don't work, I'm not sure they exist. There is a variety of super capacitors out there. I looked them up, but they are smaller than I remembered. I still think I saw some 2 Farad 5 volts at one time, but I can not prove it.

There are also some very small batteries out there. Remember the small RC cars that plugged in their base? They would run for about 45 seconds off of a charge.

My thought is make the smallest torpedo without worrying about the electronics just yet, see what is our there and what you can get by with.
 

Bernard

Joined Aug 7, 2008
5,784
I was wondering if a 7 mm prop would present a sufficent load for some of the copter motors; so made a small " boat", 5cm X 13cm, pager motor 1-AAA cell, & 8.6 mm prop, total weight-1/2 oz. When put in water RPM dropped by about half, speed 1 ft/sec. Looks like a decent load. Blades can be trimmed to fit final torp dia. Prop is yours if you want it.
[ 15 Wsec ]
 
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thatoneguy

Joined Feb 19, 2009
6,359
I guess the first thing you'd want to start with is trials in a bathtub at home or something with your battery and motor, without a timer. Use the same reed switch "safe" mechanism, but I'm wondering how you will get enough power out of batteries that you can fit into the torpedo.
 

sheldons

Joined Oct 26, 2011
613
you could try this simple circuit and play with the timing components and it could be built quite small(even smaller with smd parts),but maybe a 555 might be the way to go (using smd parts)
 

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ElectroDFW

Joined Sep 2, 2011
15
Interesting project; lots of good ideas/info.

Due to inflation, here's my 4 cents:

Re: getting power from the batteries - I would employ something similar to LED flashlights; stack the 1.5 button cells inline, use a small compression spring to hit the negative end and use the case/housing to transfer the positive terminal to the rest of the circuit.

Re: ten-second timing - perhaps pre-charging supercaps would save exhausting and replacing batteries, but I would try finding some latching reed switches (1 pole makes the connection - the other pole breaks it) and letting the loading/launching of the torp start it, then letting the juice run out to stop it.

Re: why active torpedos at all? - You prolly have more room in your ship than in the torp, so why not try a passive torpedo? think 'drinking straw **** *** [a topic disallowed in these forums]' I'm pretty sure Make: had an article about those at some point.

Just my two bits (Geez, that inflation sure is a mother!)
--Electro--
==========================
"Making one chalk mark = $1; Knowing where to make one chalk mark = $999"
- Justification of a $1000 consulting bill for mainframe support way back when
==========================
 

Thread Starter

trout

Joined Dec 22, 2011
27
@Bernard - That is a very kind offer and I appreciate you helping out like you are, but I am making a prop for this.
@ElectroDFW - There are already systems out there that use compressed air. I am trying something that will not require all the additional equipment and safety that the other system incurs.
@Sheldons - Thank you! I will consider this circuit. I am not set or fixed on a solution yet and so all ideas are being looked at.
@thatoneguy - Yes bathtub trials are the first step. Even with our subs, we start in a very safe environment before we set it in the open waters. As far as the batteries go, stacking them in serial should work.
@Bill - When you say try this, I will go and do it. Just point me in the direction you want me to go.
 
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