Posted 09 May 2012 - 04:34 PM
Posted 09 May 2012 - 05:42 PM
The simple answer is that you use a transistor.
The transistor acts as a switch controlled by an electrical signal from the Netduino.
There are a few issues to consider.
Volts and Amps
I watched the video and read the words on the web site.
They say the best voltage to use is 6V, this is because 9V can cause the igniter coil to burn too fast.
I didn't see anything to say what the current is when the igniter is turned on.
(It does say "Maximum no-fire current: 5mA" but I think that is how much current can flow and the igniter will not ignite. I am guessing this is so that the driver circuit can do a check to see if the igniters are present and wired up without heating them up.)
To chose the correct transistor you need to know how much current the igniter will take (or its resistance so we can calculate the current). Try emailing the company (or maybe I missed something).
I'm not sure if the igniters are designed to be re-used, or if they are expected to burn out and be thrown away.
I am guessing that to have any chance of re-using them, you will need to write the software to turn each one on for a short period.
You need to include something in the design to prevent the Netduino unexpectedly letting your fireworks off.
Obvious answers are a big switch, or separate removable battery (e.g. one battery for Netduino and one for igniters).
You need to be aware that the Netduino, Netduino Plus and Netduino Mini all have a feature with their GPIO pins. When the Netduino powers up, they float high - this is not enough to drive an LED, but is enough to trigger a transistor or logic circuit.
So if you just connected all the igniters to the Netduino using transistors you would probably launch all you fire works when the Netduino turned on.
I understand the new Netduino Go does not have this feature.
If I were doing this myself, I would use pairs of Netduino pins to drive opto-isolators. This requires the Netduino to drive one pin high and one pin low to turn the LED part of the isolator on. That makes it harder for a bug to cause accidental ignition, and should prevent the power up issue. The output half of the isolator is a transistor that can be used to drive a more powerful transistor for the controlling the igniter.
I think I would also look into having a change over switch to control the hot side of the firing circuit that would allow some green low current LEDs (less than the 5mA) to be connected in circuit with the igniters so you can tell that they are connected correctly.
Hopefully I have given you plenty to think about.
First thing is to find out what the igniter current is.
The second, third and fourth things to think about are safety...
- Jarrod Sinclair likes this
Posted 09 May 2012 - 08:38 PM
Circuit uses a quad opto-isolator, but only shows two igniter circuits connected.
Each opto-isolator LED has to be driven with two IO pins from the Netduino - one high and one low. (The opto-isolators are designed to be driven by logic circuits, but check that they don't need too high a current.)
The igniter side of the circuit is completely separate with its own battery.
The three way switch at the bottom controls all the current to the igniters.
In the centre position, no current can flow.
In the ARM position, current can flow through the power transistors. These will only turn on if the opto-isolator transistors are turned on. When on, the FIRE LEDs should illuminate. These need to be low current types.
In the test position, current can flow through the green "OK" LEDs to check the igniters are connected. The OK LEDs should be low current (2mA ish) so they take less than the 5mA no burn maximum. Each OK LED has a resistor to limit this current.
Note that if a higher voltage battery were accidentally connected, a higher current could flow in the test LEDs and this might exceed the 5mA and light the fuses!
Its just to get you thinking....
Posted 11 May 2012 - 10:39 PM
Posted 12 May 2012 - 06:42 AM
Posted 14 May 2012 - 09:26 PM
Posted 16 May 2012 - 02:27 PM
Posted 16 May 2012 - 08:23 PM
You will need to have a play with a fuse and see what its resistance is. (In fact you should check out as many as you have - just in case they vary a lot.) Then calculate how much current will flow from a 6V battery.
I = V / R
If its more than 800mA, then you can either take the easy option and add some power resistors to reduce the voltage a little, or use the transistor to limit the current it passes.
A transistor can be used as an on/off switch, but with the right current and voltages on its pins, it becomes like a variable resistor controlled by the current flowing into the base. (With a FET, it is controlled by a voltage on the gate.) It should be possible to design a simple circuit around the transistor that will limit the ON current to 800mA.
First find out what the typical resistance is for the fuses, and calculate how much current will flow from a 6V battery.
Remember its supposed to be fun!
Posted 08 July 2014 - 03:27 PM
This is an old thread but I'm looking at building the same. I actually want to build one (not using a net duino to start) that is more manual so that I can learn the electronics part of it.
I'm sure there are better forums to post about this but I'm not sure where to even begin.
I've ordered some electronic ignitors
They say they have the following:
Fire current: .37A Test Current 0.5MA 70degree F resistance: 1.30.15 - 1.70.15 At current length
Here is my plan.
A control box that has push button speaker connectors for connections to the electronic ignitors and then the controls would be some kind of lock out possibly a key that would not allow it to fire. And on/off rocker switch, and then light up push buttons and would be illuminated when the circuit is complete (at .05MA) to the ignitor.
This control box would have a rechargable battery (I'm thinking 12v I guess) with a way to plug it in to recharge it. All of this would be in a nice box to make it decent looking.
Having a programming background only the electronics part I'm not sure what I need to do. I'm sure I can google for most of the parts I'm looking for (push buttons, speaker connectors, wire, etc.)
I know I'll need to use resistors to reduce the current to the ignitors to .05MA but then need enough current to light the push button. Nothing more than .05MA should be allowed to the ignitor until a key is turned and the momentary push button is pressed. At that point the needed .37A would be sent to the ignitor which would launch the firework and then the circut would be gone so the push button lamp would then be off.
So any guidence on where to start reading to understand this would be great. I figure I will need to get some parts and start experimenting to get a better understanding.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users