Help with VIN Pin!!!!!

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

I am planning on getting an ardunio Duemilanove for a little project of mine: a little application (written in VB) and box (containing the ardunio Duemilanove) that can launch Model rockets.

The only problem is: most model rocket ignitors will only ignite at 9V or above. This means that 5V that is supposedly provided by the digital pins will not ignite the engines.

So my question is this: How do i get the digital pins to Provide a 9V current (Proferobly from the battery that is also powering the ardunio Duemilanove)? Do i need to Put the ignitor in-between the digital pin and the VIN pin or Put the VIn pin agross the ground.

Help please quite quickly, and thanks in advance

2

Do i need to Put the ignitor in-between the digital pin and the VIN pin or Put the VIn pin agross the ground.

Help please quite quickly, and thanks in advance

Neither of those are acceptable. To activate 9vdc to a load (your igniter) your going to have to have a switching transistor turn on controlled by an Arduino output pin via a series resistor to the base of the transistor. The transistor's emitter is grounded and it's collector lead wires to one side of the load. The other side of the load wires to + battery voltage. We would need to know the igniter's current requirements to properly size the transistor and it's base resistor.

Lefty

3

you can use this:

connect push button connections to an IO line.

4

yea the transistor is simpler and cheaper

5

Neither of those are acceptable. To activate 9vdc to a load (your igniter) your going to have to have a switching transistor turn on controlled by an Arduino output pin via a series resistor to the base of the transistor. The transistor's emitter is grounded and it's collector lead wires to one side of the load. The other side of the load wires to + battery voltage. We would need to know the igniter's current requirements to properly size the transistor and it's base resistor.

I Now have the correct data:
The ignitors we will be using "At minimum need a 9V batterys voltage and current to ignite" as described on the manufacturers website. Sorry if thats not that much use. But because of this I will be powering the arduino board and LED's on the box with with the USB's power. The Battery to ignite the ignitors will be a 9V battery (Its the cheapest/most avaleable) With that, what type/Model (NPN/PNP > Im not that good with Transistors) of transistors will I need? and if its not too much, where could i get them? I live in england so its quite difficult/expensive to get things from overseas.

6

The Battery to ignite the ignitors will be a 9V battery (Its the cheapest/most avaleable)
Ok, as long as the 9v battery can supply enough peak current to the ignitor, which is a unknow factor so far? By the way make sure you run a wire from the 9v negitive terminal to a Arduino ground pin.

With that, what type/Model (NPN/PNP > Im not that good with Transistors) of transistors will I need?

Again it depends of what the current requirement of the ignitor is, I would just be guessing without that information. An NPN is called for in this circuit configuration.

and if its not too much, where could i get them? I live in England so its quite difficult/expensive to get things from overseas.

I've been told from normally reliable sources that even in England one can obtain transistors locally. ;D

Lefty

7

im terribly when it comes to transistors myself.
relays (which I understand are less efficient) are a little easier to work with sometimes, and are more versatile.

http://cgi.ebay.com/Arduino-5V-Relay-Omron-G5LA-/280523350800?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item41507ea310

something like that would work probably better for you; atleast if you find your 9v batter isn't powerful enough, or possibly if you are using different rocket motors that need a different power source, this should always work for you.

8

I've been told from normally reliable sources that even in England one can obtain transistors locally.

Yes, we can, its a matter of the part numbers spesificly. I cant exacly go and say I need an NPN transistor and they instantly know what I need based on that small bit of information. I was looking for part numbers ext...

relays (which I understand are less efficient) are a little easier to work with sometimes, and are more versatile.

Can't use relays for one big reason. Magnets. By law mine wouldn't be allowed to be used because a stray electro-magnetic field could set them all off. also, if two are close together, the one relay could trigger the next. And, like you said - they are terribly inefficient. so no matter how easy they are to work with, its just not feasable. :frowning:

9

By law mine wouldn't be allowed to be used because a stray electro-magnetic field could set them all off. also, if two are close together, the one relay could trigger the next.

Sorry but that is just rubbish. The magnetic field from one relay can't trigger another. Magnetic fields drop off at an inverse cube rate so there is very little energy even a close distance away.

What is this law of which you speak? It certainly doesn't preclude relays.

Rocket motor ignites take lots of current in the order of several amps and a relay is the best option for this. You need a lead acid battery or something large, certainly a small PP3 will not work.

10

Sorry but that is just rubbish.

I think ist stupid too. But its what we have to cope with. If we did the insurance (Who are being really nice already, letting 10 year olds setting off rockets) would be canceled. But thats irrelevent. the fact is - With a charged 9V battery you can set off the ignitors. All they are are bits of wire with gunpowder on the end (a fuse with some explosive on it). And we use PP3's in our portable ignition sets anyway, so whats to say one wont work now (If it was such aproblem i would've mentioned it earlyer). And even if it didnt work for some compleatly unknown reason, we could just add a bigger battery.

Its OK now i have got somthing from http://www.instructables.com/id/LED-Dance-Room/step2/Circuit-Design/

I'll adapt that diagram to work with what we want...

11

And even if it didnt work for some compleatly unknown reason, we could just add a bigger battery.

Yeah, a 9V will work, but for how long? Without knowing the amperage requirements of a single igniter, we can't really know. I have read, though, that a 9V can supply 500mAH of capacity, which really isn't a lot. Plus 9V batteries are expensive.

You would be much better off in the long run to at least use a C or D-cell battery pack supplying 9-12 volts to the igniters. It will be less expensive, last longer, and give you more launches.

According to this PDF, though, for Estes igniters (which I have to assume you are using - or at least, something similar):

http://www.estesrockets.com/images/uploads/2811_Estes_Model_Rocket_Launch_Systems.pdf

...because of the extremely low resistance of the igniter, the larger the voltage of the battery, the greater the current needed (which is also going to vary depending on the length and gauge of the wire from the controller to the igniter) - and ultimately this determines how long your battery can last based on its amp-hour rating.

The bad thing about a 9V is that it might get to a point where it can't push enough current to fully ignite the igniter, but perhaps enough to start a "slow burn", that can later (a few seconds or more) ignite, shooting the rocket off. This can be a "danger factor", if you wonder why the rocket didn't go off, and approach it, then it takes of (nearly or fully "in your face"). If you or your students don't understand this, you all need to study the above PDF; in theory, you might be better off over time and safety-wise with a few D-cell flashlight batteries in series, than the simple 9-volt.

Plus you'll get to learn Ohm's Law!

:slight_smile:

12

If we did the insurance

So it's not a by law thing, it's an insurance thing. The two are totally different.

You are not by chance a school teacher in England are you?

13

You are not, by chance a school teacher from england?

No, I'm a 11 year old student.

14

If we did the insurance (Who are being really nice already, letting 10 year olds setting off rockets) would be canceled

OK so you have a lot to learn. Insurance companies are NOT really nice people. They are money grabbing bastards who will do anything to not pay out. They do this by not actually covering anything that is likely to happen. Pulse excluding a lot of stuff that they are too stupid to know about.

So it begs the question of why you need insurance in the first place. I might be able to understand it if you were a teacher who had been brow beaten over the last 30 years by successive governments to the point where anyone with any ability has left the profession and you only have idiots left but people like you are the only hope for the future.

When I was your age I was setting off rockets and making my own gun powered from stuff I bought from a pet shop.
To ignite them I was taking a torch bulb (flash light for the U.S. centric) and breaking off the glass by crushing it in a vice. then I could electrically ignite it with very low current.

Sadly I would probably be arrested if I were to do that now.

15

OK so you have a lot to learn. Insurance companies are NOT really nice people. They are money grabbing bastards who will do anything to not pay out. They do this by not actually covering anything that is likely to happen. Pulse excluding a lot of stuff that they are too stupid to know about.

I don't want to sound all rude, but just because i'm 12 doesn't mean you can call me stupid. I know that insurance people are "money grabbing bastards" because that's who are saying we cant use relays.
The point is I have what I wanted, thanks to Cr0sh, retroleftly and all the others, it may be enough to secure our inovation prize. Thanks!!! :slight_smile: :slight_smile: :slight_smile: :slight_smile:

16

Fine first off I didn't call you stupid it was the insurance companies I was saying were stupid.

In post 13 you said you were 11 and now in post 15 you say you are 12. Have you had a birthday?

17

One and two are together on the keyboard. I am 12

18

One and two are together on the keyboard. I am 12

A word of unsolicited advice: In the future, post your age or grade level in your first post; I too thought you were likely a school teacher or other adult from England. When I was 12, the concept of "insurance" wasn't even something I was aware of, let alone something I talked to others about.

Then again, I'm an American with a public school education, and we didn't have the internet publicly available back in 1985...

;D

It just would've cleared the air a bit to know exactly who we were speaking with. What I do wonder, though, is exactly how you are in contact with "insurance people"? Its not like they can legally interact with minors (unless laws are really different over there; here in America, you would need to have an adult present, the minor couldn't enter into contracts, etc).

Is this part of a school project or something? In other words, how is it that insurance is even involved, let alone dictating something as minor as the switching system used for model rocket launches...

I also find it funny that they think a relay is worse than a pushbutton switch; with this level of competence, its going to be a fun world as we continue to get closer to the Singularity...

:stuck_out_tongue:

19

Is this part of a school project or something? In other words, how is it that insurance is even involved, let alone dictating something as minor as the switching system used for model rocket launches.

Yes.
The teacher is in-charge of the students, and the insurance says to the teacher that we need to launch responsibly, and have as much control as possible at all times. This includes control in freak events, such as a misfire, Loss of power, Possible outside variables... the list gos on. That makes it the teachers responsibility to check that everything is fine before take-off, including the launch equipment. If said teacher doesn't check or checks and notices there are relays in the circuit but continues then the teacher was being negligent, and so they could say that in event of an accident the teacher wasn't following the insurance, and so they wouldent have to pay up, like Grumpy_Mike said.

When I was 12, the concept of "insurance" wasn't even something I was aware of

Its a sad age, isn't it