Camera flash discharge switch? - Page 1
Forum section: electronics / beginners

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 02, 2015, 05:09:25 pm
content: I am designing a solar powered cannon for an engineering project. I am planning on charging a cap using a camera flash, and then dumping it into a coil. Anyone know what I can use that wont take much/any power to trip? The machine needs to fire after the light is removed. The switch needs to be able to handle a 250v+ discharge across a coil and not explode. Thanks for the help!

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 02, 2015, 06:06:22 pm
content: camera flash (abttery powered) works based on stepup transformer and IGBT/thyristor and PWM generator so thats what you need. to discharge through xenon tube, another small stepup transformer will be needed up to tens KV to breakdown the xeon gas. but i dont think thats applicable for your cannon project... its canon to shoot bullet right? not canon to shoot photo?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 02, 2015, 06:19:29 pm
content: They are really a rediculusly cheap board that I found. I just need to dump the cap into a coil after 30 seconds instead of exciting the xenon tube. And yes, it is shooting a steel rod.

author: edavid
author_rank: Super Contributor
timestamp: April 02, 2015, 06:31:52 pm
content: A power FET is the simplest solution... but I don't think the cap on that board will store enough energy for a coil gun.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 02, 2015, 06:38:07 pm
content: transformer in red tape is the most important part, next to it in blue? is the xenon activator transformer you are not going to need it, xenon tube also no need. the transistor and other passives probably the pwm/sine/astable generator, trace and learn from that. once the cap is full, you can mod to add igbt to the coil. the cap looks small, a medium power mosfet/bjt probaly works.

author: dmills
author_rank: Super Contributor
timestamp: April 02, 2015, 08:34:55 pm
content: IGBT?What is wrong with a thyristor for this application, it is only going to be a few hundred volts, and the coil will limit di/dt?But you are going to need massively more capacitor, there is a reason serious magnetic cannon use compensated alternators instead of cap banks!Regards, Dan.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 02, 2015, 09:24:19 pm
content: Well, does anyone else know the best way to launch a ping pong ball using a 20cmx20cm solar panel for 30 seconds? It needs to have no stored energy before the light is turned on.

author: edavid
author_rank: Super Contributor
timestamp: April 02, 2015, 11:31:31 pm
content: Use a motor to wind up a spring or rubber band?

author: westfw
author_rank: Super Contributor
timestamp: April 03, 2015, 06:15:17 am
content: One thing you might try is using the flash tube itself as the switch. You already have a relatively low-power trigger circuit for the tube, and if you put your coil in the gnd side of the flash tube, a good chunk of current will flow when you fire the tube...

author: Ian.M
author_rank: Super Contributor
timestamp: April 03, 2015, 07:16:32 am
content: You'll be lucky to be able to do anything useful with that under artificial light.The maximum output of a high efficiency 20x20 cm solar cell under direct desert sunshine is about 8W. The brightest artificial lighting commonly used (TV studio lighting) is about 100 times weaker than direct sunlight, so you'll probably be getting no more than 80mW for 30 seconds = 2.4 Joules.That's *BARELY* enough to charge a typical 120uF ex-disposable camera flash capacitor to 200V if every part of the system had 100% efficiency, which it certainly wont have.The open circuit voltage and short circuit current of the panel to be used under the actual lighting conditions of the competition would be very useful numbers to have.You certainly DON'T want to be shooting a steel rod out of a coil with your minimal energy - you need *MUCH* better coupling to the 2.7 gramme pingpong ball than that can provide. You may want to look at induction coil gun designs and use an annulus cut out of aluminium foil to couple the magnetic field to the ball with minimum extra mass.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 03, 2015, 07:35:19 am
content: Quote from: westfw on April 03, 2015, 06:15:17 ammuch energy will be lost in light and heat. if he put larger capacity cap, he will overstress and kill the tube much earlier.

author: Seekonk
author_rank: Super Contributor
timestamp: April 03, 2015, 08:27:22 am
content: An engineering project should have some engineering terms. Do you only get 30 seconds to charge from solar or does the object have to stay airborne for 30 seconds? You sound totally clueless. Is this how you will get through school, having others do your work for you?

author: Ian.M
author_rank: Super Contributor
timestamp: April 03, 2015, 08:57:11 am
content: A sort of hydrogen spud gun might do better.Generate hydrogen and oxygen by electrolysis directly in the chamber of the gun which could be shaped to fit fairly closely to the pingpong ball and have an O ring seal to the ball just shy of its equator so it pops out really easily, + a close fitting stubby barrel a few inches long. Detonate it with a very small spark.It will need a MPPT DC-DC converter to get the best out of the electrolysis cell and a much much smaller boost converter and spark generator.As the mass of gas will be a very small fraction of the mass of the ball, if the barrel length is correct, most of the energy available will end up in the ball.You lose some to the heat of vaporisation of the water as the combustion products end up as steam, not water.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 03, 2015, 02:39:48 pm
content: Thanks for the ideas everyone! Sorry about the vauge details about the 30 second thing. The light source is turned on for 30 seconds. Details can be found here if anyone is interested:https://www.sdstate.edu/engr/camps/expo/cannon.cfmAs for the original idea, does anyone think that the coil gun would even work at all? Or should I wind up a spring or something? The hydrogen cannon seemed like a neat idea, but the device needs to be electrical or electromechanical. Again, thanks for all the suggestions! I really apreciate it.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 03, 2015, 02:41:29 pm
content: Quote from: Seekonk on April 03, 2015, 08:27:22 amSorry about being totally clueless about the details. As for getting through school, I am doing terrible, thanks for asking.

author: jlmoon
author_rank: Unknown
timestamp: April 03, 2015, 02:58:34 pm
content: Getting through school takes plenty of STUDY, PERSEVERANCE and a true PASSION for the field of study.

author: Ian.M
author_rank: Super Contributor
timestamp: April 03, 2015, 07:16:55 pm
content: Quote from: iamdarkyoshi on April 03, 2015, 02:39:48 pmThere are absolutely no details about the light source except that it can be switched on for 30 seconds with uniform brightness and off again which rules out any lamp with a significant warmup time. I think we can probably rule out single cell Maglites or 16KW Klieg lights @ 1m - if only because the former couldn't produce enough energy to lift the pingpong ball by its own diameter and the latter would probably melt the student's device and the transparent enclosure, but without any idea of the available light intensity, you are either simply playing roulette or are going to have to design a modular system with plug-in energy storage units and a range of power conversion modules so you can rapidly adapt to conditions on the day.I suspect an electromechanical solution will win. Probably a spring driven hammer with an effective mass at the head of 2.7g so the greatest possible proportion of its momentum is transferred to the pinpong ball. Obviously either a high effficiency PM motor or a solonoid actuator + a ratchet will drive the spring tensioning mechanism. This is most likely to scale well with an uncertain power budget.If you were still looking at coil guns, consider a rare earth magnet glued in the end of a Mcdonalds straw as the piston, which should be carefully ballasted to 2.7g and arranged to impact the pinpong ball at end of stroke for maximum momentum transfer. I'd use a very thin bamboo skewer coated with PTFE dry lube as a central spike to stabilise it in the work coil before firing with a PTFE ring in the piston just behind the magnet and a fixed ring at the base of the spike to locate it on so that once the piston moves its essentially free.Any other electrical system is going to waste energy propelling the sabot that will be required to couple to the pingpong ball (unless you are allowed to silver plate it).

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 04, 2015, 07:43:53 pm
content: Quote from: Ian.M on April 03, 2015, 07:16:55 pmThank you very much for the help! I do have some leftover PTFE tube from my 3D printer.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 11, 2015, 01:18:55 am
content: As per Ian's advice, I have shot rare earth magnets weighing about 2.6 grams from the cannon. Unfortunately, every MOSFET I try seems to go short after two shots. For now, I am testing using my Frankenstein switch. The video can be seen here: Camera flash coil gun:http://youtu.be/n3VKA64Psk4Battery is 1.5v and it draws 1.3-0.8A as it charges to 250v. I have wired two of the circuits in parallel after I had sketched them using a pirated copy of DaveCAD. Only the HV portion of the circuit is used. It surprised me how far the magnets launched off of only ~1.5 watts for 30 seconds. Anyway, as for the MOSFET: the capacitor's positive is on the batteries' ground, so when I used the MOSFETs, they needed to be switched using an external supply. That is, of course, before they shorted out. I wonder if the inductor is sending a spike through the cap and then into the MOSFET that kills it? My last MOSFETs were 3x IRFP460LC MOSFETs in parallel.

author: Ian.M
author_rank: Super Contributor
timestamp: April 11, 2015, 02:37:25 am
content: If you don't show us the schematic of the coil and discharge section, there's not much we can do to help with the MOSFET problem. You *COULD* simply make them pluggable and treat them as consumables, but that gets expensive if you need to do a lot of testing.Have you tried letting the magnet hit a pingpong ball just after its left the coil? If their masses are equal, the magnet should pretty much stop dead and the pingpong ball should go flying off. I'd be interested to know how far it goes.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 11, 2015, 08:10:48 am
content: Quote from: iamdarkyoshi on April 11, 2015, 01:18:55 amexactly! use protection diode, google diode protection for mosfet. i managed to short few mosfets albeit with protection diodes everywhere, must be wrong type of diode, use fast acting voltage suppression diode or scothky i guess, i have few in stock but reluctant to use due to limited number i have 10 only and each mosfet can have as much as 3 protection diode.

author: Zero999
author_rank: Super Contributor
timestamp: April 11, 2015, 03:51:59 pm
content: Is the light source available to you for testing? If not, you need to ask them to provide you with more information.

author: Zero999
author_rank: Super Contributor
timestamp: April 11, 2015, 04:11:38 pm
content: Or a MOSFET + BJT cascode, combining the switching speed of a MOSFET, with the high voltage rating of the BJT.The MOSFET can be a very low R-on type but it only needs to be rated to 10s of volts.The BJT needs to be rated to the full voltage though.It's better if the bias voltage is lower than the MOSFET's gate threshold voltage but it needs to be considerably above the base-emitter saturation voltage of the BJT.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 11, 2015, 06:59:46 pm
content: Quote from: Hero999 on April 11, 2015, 03:51:59 pmFrom what I have heard, the light source is a 60w incandescent. I will probably call them for details when I am not at school, my job, or my other job. Honestly though, if I can get 2 watts from the light using some 1" x 2" cells I just purchased 50 of, it should surpass what the circuit in the video did. Although I won't use all 50, I probably have other uses for the rest on other projects.

author: kolbep
author_rank: Frequent Contributor
timestamp: April 11, 2015, 07:33:22 pm
content: Some mini compressor that can run off the panel. Maybe an air pump from a fish tank, or windscreen washer pump, etc. You have the ball wedged in the end of a tube, and held in by a solenoid pin when receiving power.So when the light is on, the pin engaged, and the pump starts to build up pressure on the pipe that is blocked by the ball.When light is turned off. The solenoid looses power, the pin is retracted by a spring, and the ball is pushed out by the air pressure..

author: Zero999
author_rank: Super Contributor
timestamp: April 11, 2015, 07:46:06 pm
content: 2W sounds like a lot from a 60W incandescent lamp.

author: Ian.M
author_rank: Super Contributor
timestamp: April 11, 2015, 08:14:01 pm
content: If that's the case that its a 60W incandescent, you are FUBARed before you even begin.In direct sunlight a 20cm square ultra high efficiency (20%) monocrystalline Silicon solar cell could produce as much as 8W. However that's noon desert sunshine which is near enough 1KW/m^2, with the panel square on to the sunlight.A 60W incandescent bulb is only about 15% efficient. The other 85% is wasted as heat. If you can intercept ALL the light emitted, with a solar cell you can get 20% of that 15% or 1.8W. However you are restricted to a 20cm square and are likely to be at least 50cm from the filament so you have 0.04 m^2 of a spherical surface at radius 0.5m (area 3.1415 m^2) so you've only got 1.27% of the total light output to work with. Even if I'm charitable and grant a reflector that directs five times as much light at the experiment box, that's only 6.4%. or 115mW. Applied for 30 seconds, that's under 3.5 Joules, and a 120uF cap charged to 250V has 3.75 Joules energy.You almost certainly haven't got enough power to fully charge the cap even if your circuit is 100% efficient.You urgently need to confirm the lamp type and power, the distance from the lamp o the box, and what area it fully illuminates at that distance. I suspect you are either going to have to get a smaller capacitor or drop the max voltage and redesign your coil accordingly.@Kolbep: The problem is the energy lost as heat compressing the air, friction at the seal between the ball and the tube, and energy lost as residual excess pressure release when the ball clears the tube. If one wanted to go mechanical, a spring loaded hammer is a far better bet, wound back by a motor acting as a winch and released by cutting a thread with a solenoid and some razor blades.

author: Zero999
author_rank: Super Contributor
timestamp: April 12, 2015, 01:14:14 pm
content: Quote from: Ian.M on April 11, 2015, 08:14:01 pm15% efficiency still sounds very optimistic for an incandescent lamp. It depends on the part of the spectrum you're interested in. For illumination 400nm to 750nm is the important part, any radiation outside this is considered to be wasted energy. Solar cells have peak efficiency in the near IR (750nm to 1100nm) which is a better match to incandescent lamps so it may not be that bad.Another thing to bear in mind is it's energy not power you're interested in, so even if the solar cell only outputs 100mW, that can be stored over 30 seconds and power a launcher which may take 30W for 100ms.

author: Ian.M
author_rank: Super Contributor
timestamp: April 12, 2015, 04:18:02 pm
content: Yes, I used very optimistic figures, assuming a high efficiency halogen lamp, solar cells that are either extremely expensive or still in R&D, a very good reflector, no wasted area that could have silicon on it etc. The point was to show that the power budget is insufficient even with the optimistic assumptions.I think this is going to be won by whoever's pingpong thrower is the best at adapting to insufficient power on the day. A high efficiency mechanical spring based hammer mechanism + accumulating the 'solar' energy at whatever rate it comes in till there's enough to ratchet back the spring another click is almost certainly the best bet. It should adapt the accumulation time to allow for the increase in spring tension as it progresses.Trying to match a coil of particular length and resistance to varying capacitor voltages or switching in or out capacitors to make it possible to reach the same voltage is a nightmare. It could be done with multiple coils fired in sequence till all the available energy is used, with energy recovery from the just fired coil after the magnet has cleared it, but with such a small energy budget, I suspect the more complex control system's consumption would wipe out any advantage.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 14, 2015, 01:33:52 am
content: Good news! The light source is four 125w floodlights. Much better. Nearly 10 times the wattage.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 14, 2015, 08:00:53 pm
content: Even better news! My panel is about half built, and I was able to get 820mW from the panels (820mv @1A) and I was only using a 60W lightbulb! The circuit draws 2A at a 50% duty cycle (first time using a scope!) when operated at 1v.

author: Ian.M
author_rank: Super Contributor
timestamp: April 15, 2015, 12:11:53 pm
content: Inverse square law: The light intensity falls proportionately to 1/(r^2) so a 60W bulb at distance r will give you more output than four 125W bulbs at distance 3r (ignoring reflectors and anything else tat concentrates the light.You need to know the distance from the panel to the lights, then if you test with one 125W light at half that distance you'll have reasonably good figures. If you underestimate the distance, you will find yourself with a serious power shortfall + light output is very sensitive to line voltage so for optimum results your circuit is still going to need to be able to handle a 2:1 variation of available power and make the best use of it.A tapped work coil(to allow the load to be adjusted depending on the capacitor voltage)is possible but difficult as taps past the one you actually ground to fire will swing negative but must not be allowed to pass current so you need semiconductors that can stand off a large AC voltage. TRIACs can do this, but they have problems with excessive dI/dt at turn-on and excessive dV/dt can cause false triggering so careful selection + some experimentation woyld be required.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 16, 2015, 05:15:14 pm
content: So I tested it using a 500w light four feet away from the panel for 30 seconds and it launched the ball a good 25 feet @150v. Now I need to find a way to switch a mosfet on this thing. I am at school right now, but I will be posting the DaveCad drawing of the circuit in a bit. The problem is that the capacitor's positive is common with the solar panel's negative. I need the mosfet to switch as soon as light is removed.

author: Zero999
author_rank: Super Contributor
timestamp: April 16, 2015, 08:34:54 pm
content: Why not use an SCR rather than a MOSFET? They have lower on losses than MOSFETs at high voltages and only need a single pulse to trigger.The gate could be connected to the anode via a high value resistor and shorted to the cathode via a small BJT while the power is on. When the power is disconnected, the BJT will turn off, causing the gate to receive a trigger pulse.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 17, 2015, 03:08:53 am
content: Quote from: Hero999 on April 16, 2015, 08:34:54 pmI generally do not purchase parts anymore, I find them in my scrap pile. Got any recomended place to find an SCR? Where are they commonly found? I really apreciate everyone's help here. This forum is awesome.

author: pickle9000
author_rank: Super Contributor
timestamp: April 17, 2015, 03:23:00 am
content: Quote from: Hero999 on April 16, 2015, 08:34:54 pmThat's the classic way.

author: SeanB
author_rank: Super Contributor
timestamp: April 17, 2015, 04:30:35 am
content: Use a triac instead if using used parts, most commonly used in a light dimmer. Just using it as a SCR will work as well.

author: Ian.M
author_rank: Super Contributor
timestamp: April 17, 2015, 07:08:41 am
content: It will also need a scheme to provide a pulsed current to trigger it. High current TRIACs with a high surge capability are usually not very sensitive so Hero999's idea of a permanently connected gate pullup with a shorting transistor to the cathode will either waste too much of the limited power available or not trigger reliably.

author: Zero999
author_rank: Super Contributor
timestamp: April 18, 2015, 03:44:42 pm
content: Quote from: Ian.M on April 17, 2015, 07:08:41 amSimple: add another transistor between the gate and anode to increase the sensitivity.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 20, 2015, 07:56:07 pm
content: Well this just got harder... the mechanism will need to fire on its own, the lights will stay on. I might just use the hv capacitor with a voltage devider and just connect it to a mosfet. Im thinking to use mosfets to provide a sharp trigger. I could not find any SCRs or TRIACS.

author: Zero999
author_rank: Super Contributor
timestamp: April 20, 2015, 07:59:37 pm
content: That's fairly easy. Use a DIAC to fire the TRIAC, once a specified voltage on the capacitor has been exceeded.TRIACs and SCRs are widely available. Where do you live?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 20, 2015, 11:45:33 pm
content: Quote from: Hero999 on April 20, 2015, 07:59:37 pmUSA, but the competition is in 4 days.

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2015, 08:11:06 am
content: Quote from: iamdarkyoshi on April 20, 2015, 11:45:33 pmThen you've not allowed yourself enough time for this. Three weeks (based on the date you started the thread) is not enough.Isn't there a RadioShack in your area?DIACs and TRIACs can also be found in light dimmers.Another possibility is Digikey and pay extra for express shipping.

author: Ian.M
author_rank: Super Contributor
timestamp: April 21, 2015, 09:26:33 am
content: Try to get a TRIAC with DIAC trigger circuit put together today, Scavenge the parts you need from a light dimmer. A smallish auxiliary capacitor + a high value resistor to charge it off the main flash boost converter output should be added. The DIAC is connected from the aux. cap to the TRIAC gate (with a 100R current limiting resistor) and when it reaches its breakover voltage it discharges the aux cap into the gate firing the TRIAC. Timing is set by the aux cap value and its charging resistor.If you cant get that going by tomorrow morning, its too late to fix your circuit so you had better get a handful of the MOSFETs your circuit is blowing and fit a socket so you can change them quickly. Your remaining problem is triggering it after 30 seconds (or as long as they give you per shot) with the lights staying on. For simplicity and ruggedness, I'd use a CMOS 555 timer. Its generally not a good idea to use large electrolytic capacitors in a 555 timer circuit, because the time is highly dependent on the capacitor's leakage current, but you should get away with it for timing up to a minute or so. The 555 will need a supply, ideally about 12V to drive your MOSFET. I'm not sure whether a Joule thief style boost circuit running off your main solar panel, or auxiliary panels round the sides of the 20cm cube, would be the best choice. Put the 555 in a socket and get some spares as the MOSFET blowing is likely to take out the 555 as well.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 21, 2015, 04:52:23 pm
content: Quote from: Ian.M on April 21, 2015, 09:26:33 amI do know where some dimmers are, but what about diode protection? The spike from the coil is what kept killing my mosfets. Also, a 555 wont work beacuse we cant have an external/stored power source and my panel runs at about 1.2v. I will try the triac/diac combo, but how should I protect it?

author: SeanB
author_rank: Super Contributor
timestamp: April 21, 2015, 06:13:40 pm
content: Triac will most likely not need protection, it is a pretty rugged device. The only way to kill them is with either massive overcurrent for a single pulse, sustained overcurrent for long enough for the die to melt, voltage high enough to trigger it into conduction with the subsequent overcurrent or giving the gate too much current for long periods leading to localised overheating.Other than that they protect themselves quite well, too high a voltage across terminals and it turns on, too fast a rate of rise and again turns on. Basically they really want to turn on, and when on are pretty rugged, though often they will kill the load.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 21, 2015, 11:36:13 pm
content: Quote from: Ian.M on April 21, 2015, 09:26:33 amOkay, I have taken apart the only thing I could find with a triac. My dead lab supply I got from school. The output never does stays stable on it, and all it is is a dimmer and transformer. The TRIAC is a BTA06, and for the DIAC, the same board has a DB3 diode, which appears to be a 32v trigger diode for use with TRIACs. I will try to put something together, and post an update once I do.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 22, 2015, 02:42:05 am
content: Oh my gosh, it works!!! Even though this was battery tested, I can always change cap/resistor values for the panels on competition day.https://youtu.be/dfFdHPdYFq0With craptastic meters, this kind of thing is an explosive jack-in-the-box. It startles me every time it launches

author: Zero999
author_rank: Super Contributor
timestamp: April 22, 2015, 11:55:29 am
content: Congratulations. What circuit did you use?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 22, 2015, 12:35:28 pm
content: Quote from: Hero999 on April 22, 2015, 11:55:29 amA DIAC triggered TRIAC with a secondary capacitor. You guys are genius. And, I learned about DIACS and TRIACS during this project. Today at school I will build the actual box that this is contained in.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 23, 2015, 03:15:09 am
content: Here ya go everyone:https://drive.google.com/folder/d/0B-LjUeh-cirIelgxbzVFYnRiTHM/editPoogle Docs seems to have compressed my images... Then again so does the forums...The warning sign is there as both a warning, and to strike fear into my oponents or something. The breadboard lets me change cap values for different times so I can calibrate when I arrive. I have also fitted a switch in the launch rail that disconnects the panels once the ball has left. So far it can even charge and fire off of my house lights and my 75w lamp from two feett away sends it across the room.

author: Zero999
author_rank: Super Contributor
timestamp: April 23, 2015, 09:04:05 pm
content: The TRIAC's gate could do with a series resistor (330R would do) otherwise the capacitor discharging into it could damage it.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 24, 2015, 12:23:31 am
content: Quote from: Hero999 on April 23, 2015, 09:04:05 pmWhoops, I forgot to add that to the DaveCAD drawing. I have fitted a 100R resistor on mine. Thanks for the reminder though. All of my tests today with a handheld light were +/- 1ft on the landing area and it hasnt misfired at all, aside from when I forget the magnets

author: Zero999
author_rank: Super Contributor
timestamp: April 25, 2015, 07:47:09 pm
content: Did it work on the day?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 25, 2015, 08:18:51 pm
content: Quote from: Hero999 on April 25, 2015, 07:47:09 pmWe got first!!Mainly because my school had the wrong size ball, and they wanted to use their ball. They brought regulation balls, but used some blue ball that were roughly the same size, but didnt have any compressed gas inside. However, on my first run, they let me use mine and take 10% off of my distance. The second place winner was a mousetrap and motor, and if they had used a real ping pong ball, it probably would have won. But anyway, thanks a whole lot evernyone! The judges said this is exactly the design they have been waiting for since the first match 10 years ago. Everyone just uses a motor and spring.