I was recently looking into making or buying a blasting machine, to safely test EM from a distance. Alot of the commercial machines cost over 400 usd,
and with my very little knowladge on electronics, making it didnt seem to be the best option either. As of now i use a estes ignition system but that
only seems to work so well.
But i came up with a thought when watching TV. So you know those Dr. Ho ads. Well what if his pain therapy system had an electrical output, great
enough to make high resistance wire heat up enough to, ignight a pyrotechnic mix.
So i did some research. And i found out the output is infact high enough to set off an Ematch! Not just one but 5!
Does anyone have experience using a Dr. Ho Pain Therapy System as a 4 shot blasting machine? And if so how did it turn out? roXefeller - 27-12-2020 at 16:27
What is your source for that 5 match estimate? What are your specs of the ematch you are using? What is the output impedance of the machine?DBX Labs - 27-12-2020 at 19:48
Dr. Ho's system costs upwards of $100, however, there are cheaper options.
I recommend you take a look at a couple of videos I published recently; it doesn't require extensive knowledge of electronics to hook a drill battery
up to some cable and nichrome.
Be careful. I don't recommend attempting to emulate either if you don't have a good idea of the danger of capacitors.foreign maple - 28-12-2020 at 19:06
What is your source for that 5 match estimate? What are your specs of the ematch you are using? What is the output impedance of the machine?
my estamate is based off the resistance of those glass christmas tree lights 8 ohm. The output is fairly
high 12v i think. This should theoretically set off five improvised ematches in series reliably. roXefeller - 28-12-2020 at 19:12
Output impedance in a necessary input. How much does the output voltage drop as you draw amps for those 8 ohms?foreign maple - 28-12-2020 at 19:22
Output impedance in a necessary input. How much does the output voltage drop as you draw amps for those 8 ohms?
i am not entirely sure. This was more of a joke than anything. I am not exactly sure of the specs but i have tried using it before
just as a joke to see if it would work and it did. I am not entirely sure on the specs though roXefeller - 28-12-2020 at 19:42
Sorry to throw that out without more description. We describe the output of an energy source with impedance. Sure it can produce so many volts, say
12V, but that is with an open circuit, like with a voltmeter. But when we put a load on it, some internal resistance causes voltage drop. Say it has
an impedance of 0.5 ohms. If you start drawing 4 amps to feed your load, 4*0.5ohms is 2V drop, so you actually can only put out 10V at that load.
The short circuit output comes from 12V/0.5ohms = 24amps, so it's limited even when we short it. Quality batteries have very low impedance and can
kill a person. This topic can be described as Thevenin circuits.
Cattle fence chargers are typically high impedance to not kill people or animals, just a high voltage and milliamps of current for effect. Low
impedance chargers are easy to rig but easy to kill. Capacitors have very low equivalent series resistance, hence their danger.
There is a theory of maximal power transfer that can be derived by looking at internal impedance and external impedance (the ematch). It's a quadratic solution.
Basically maximum power out comes when the equivalent load (series parallel whatever) is matched to internal resistance. But you have some practical
trial to say it works, so that's neat.foreign maple - 28-12-2020 at 19:49
Thank you very much! I am looking into researching more about the theory of electricity. It has always interested me but i have never knew very much
about it. But i allways want to learn more. Nitrosio - 29-12-2020 at 05:48
roXefeller - 29-12-2020 at 18:15
Nitrosio, did you design that yourself? Looks like an RC blast circuit, yes?Vomaturge - 30-12-2020 at 19:52
Looks to me like it just generates an elevated voltage (possible as high as 40v) from a 5v battery. Then it charges a 10000 uF capacitor and when you
push the other button it closes a relay and delivers the 40v, 8j max into the load of your choice. Not sure how this is better than using a big
rechargeable battery, in either case the biggest impedance (limitation on current flow) will probably be either the e match itself or the wire
connecting it to your controller. Same goes for the shock device the OP recommended.
For every "improved" controller, you have to ask yourself if it makes things more reliable, safer, gives you options to control multiple fireworks in
a specific order, lets you run a thinner wire further, removes the need for batteries, etc. Otherwise, more steps will only make it more likely to
break or to be confusing to operate.
PS. I wonder if you could light off some thermite with a 1mm nichrome wire and sufficient current?
PPS isn't it better to put e-matches in parallel whenever the wire/controller can handle such a low resistance load? I'm not sure how consistent the
ignition time is for these, but if one series e match ignited and came loose during lift off, it would put any others that had not yet fired out of
comission, right? I'm no expert here, so that's just conjecture.
PPPS just remembered this. apparently it can be a problem, but it really depends on the e match construction, delay time, and consistency
[Edited on 31-12-2020 by Vomaturge]wg48temp9 - 30-12-2020 at 23:25
The circuit displayed above contains a x5 multiplier circuit. The NE55 has about two base emitter voltage drops in its about followed by two more base
emitter voltage drops in the driver stage. So the voltage swing of the output stage could be as low as 2.6V. Lets be generous and say its 3.5V. So
ignoring the voltage drops and leakage/capacitance in the diodes, the output voltage swing would be 17.5V. Each of the 8 diodes in the cascade stage
would drop a voltage of about 0.6V. Thats a total of 4.8V making the output only about 12V and less than a joule of energy in the capacitor.
It would be a lot simpler to just use one or two 9V batteries in series with a push button perhaps with a parallel capacitor to increase the pulse
current.roXefeller - 31-12-2020 at 07:59
I don't know about you, but when I was lighting off estes rockets as a kid I would get different ignition delays as the batteries deteriorated. From
reading old patent literature, RC discharge circuits were developed to introduce consistency and reduce the number of failed ignitors in a
multi-ignitor shot. It's easier to predict the discharge amperage from a capacitor discharge than a partially used, or new old stock battery.
I'll have to grab my blaster's handbook to review the choices of parallel vs series vs series-parallel. It has to do with what equivalent load
impedance the RC circuit is rated for IIRC.Fulmen - 31-12-2020 at 11:52
It's as simple as that, fitting the impedance to the power source. Ideally you would have all igniters parallel as failure mode will be a break. Yamato71 - 30-1-2021 at 18:13
Commercial blasting machines of the 10 cap variety usually generate 90-150 volts DC at a relatively high current. The high voltage quack medical
device referenced above uses a 5V supply with an 8 stage voltage multiplier and generates 50 volts at a few milliamps at best. For what you want to
do, I can think of three options.
1. Motorcycle batteries. These are usually 6 or 12 volts but can source many amps into a low resistance. For multiple caps, tie two or more
batteries in series.
2. eBay. Used blasting machines can be had very reasonably.
3. Old camera flash. If you can find an old style xenon flashlamp style camera flash in a thrift store, the power supply will generate 200-400 volts
at several amperes, depending on the power of the unit. Be careful, these things bite.
