Just the sort of info I am looking for. I can add a little about burning out coils. The coil material is probably a Nickel or tungsten alloy chosen not to oxidise too fast .This has a high positive temperature coefficient, a bit like a light bulb. So for a reasonable overload its resistance increases with the extra heat and it self regulates. But go too far and its game over.
Just the sort of info I am looking for. I can add a little about burning out coils. The coil material is probably a Nickel or tungsten alloy chosen not to oxidise too fast .This has a high positive temperature coefficient, a bit like a light bulb. So for a reasonable overload its resistance increases with the extra heat and it self regulates. But go too far and its game over.
Have posted a quick video (here and in the media section) to show a delay timer to simulate engine start-up. The timer is in the line to the air pump (powered from a 2s LiPo along with the smoke pen) and is set to delay the air, to allow the smoke to build up in the pen first. Graham has a similar set-up, but it's a bit fancier, being done with his own electronics.
JB
Have posted a quick video (here and in the media section) to show a delay timer to simulate engine start-up. The timer is in the line to the air pump (powered from a 2s LiPo along with the smoke pen) and is set to delay the air, to allow the smoke to build up in the pen first. Graham has a similar set-up, but it's a bit fancier, being done with his own electronics.
JB
Tim,
I haven't deliberately tested to destruction, but I have abused the heating coil during development. On the whole, I have tried to keep the coil operating conditions as close to the normal use as an e-cig, i.e. wick wet with smoke fluid and an air flow over the wick/coil. To reduce the risk of the wick running dry, I expanded the smoker fluid storage by adding a reservoir tank to the original e-cig reservoir. The new tank is made from acrylic tube I had in my 'useful bits' box. It is important that the reservoir is airtight, otherwise the wick floods. The filler hole is closed off with a caphead screw and o-ring. JBkiwi has recently demonstrated a refillable reservoir with a pump to keep it topped up.
I'm sure that without fluid, the coil will heat up more, and would, if it gets hot enough burn out. That will depend on how much current is being passed through it. I have let some of mine run dry without failure. The e-cig housing does get warm, but not too hot to handle. I assume this is also the case when used for it's original intended purpose. So not so hot that it would cause a fire, unless the current is set too high, in which case the coil would likely burn out quickly removing any risk of fire.
There are different coils available, with different electrical characteristics. The ones I am using draw a current of around 1A on 3V. I make sure that any electronic drivers I am using have a current rating way in excess of that, so haven't had any failures due to the coil running dry or burning out.
For the gunfire simulation I do run the coil continuously with no air flow for much of the time. That way there is plenty of smoke to blow out of the e-cig when the air pump is switched on. I haven't had any coil failures with this. The only coil I have destroyed occurred when I accidentally applied a fully charged 2S LiPo direct to a coil. It vapourised within milliseconds!
Graham93
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I haven't deliberately tested to destruction, but I have abused the heating coil during development. On the whole, I have tried to keep the coil operating conditions as close to the normal use as an e-cig, i.e. wick wet with smoke fluid and an air flow over the wick/coil. To reduce the risk of the wick running dry, I expanded the smoker fluid storage by adding a reservoir tank to the original e-cig reservoir. The new tank is made from acrylic tube I had in my 'useful bits' box. It is important that the reservoir is airtight, otherwise the wick floods. The filler hole is closed off with a caphead screw and o-ring. JBkiwi has recently demonstrated a refillable reservoir with a pump to keep it topped up.
I'm sure that without fluid, the coil will heat up more, and would, if it gets hot enough burn out. That will depend on how much current is being passed through it. I have let some of mine run dry without failure. The e-cig housing does get warm, but not too hot to handle. I assume this is also the case when used for it's original intended purpose. So not so hot that it would cause a fire, unless the current is set too high, in which case the coil would likely burn out quickly removing any risk of fire.
There are different coils available, with different electrical characteristics. The ones I am using draw a current of around 1A on 3V. I make sure that any electronic drivers I am using have a current rating way in excess of that, so haven't had any failures due to the coil running dry or burning out.
For the gunfire simulation I do run the coil continuously with no air flow for much of the time. That way there is plenty of smoke to blow out of the e-cig when the air pump is switched on. I haven't had any coil failures with this. The only coil I have destroyed occurred when I accidentally applied a fully charged 2S LiPo direct to a coil. It vapourised within milliseconds!
Hi Graham,
I've been following the smoke generator with interest. I've been experimenting using a wick and a vaping coil. The wick is obviously in a pool of fluid. I have only used for short periods of time but it does give of copious amounts of "smoke". What I would like to know is , have you tested your system to destruction? By that I mean, what are the consequences of running out of fluid but still having a hot coil? Does the coil get hotter and hotter or burn out? or does the fault go further back up the system and ruin expensive electronics or is it likely to cause a fire in the boat? As I say I have a simple effective system but haven't had the time to do destructive testing. Any thoughts on the matter are greatly appreciated.
best wishes Tim
Hi Graham,
I've been following the smoke generator with interest. I've been experimenting using a wick and a vaping coil. The wick is obviously in a pool of fluid. I have only used for short periods of time but it does give of copious amounts of "smoke". What I would like to know is , have you tested your system to destruction? By that I mean, what are the consequences of running out of fluid but still having a hot coil? Does the coil get hotter and hotter or burn out? or does the fault go further back up the system and ruin expensive electronics or is it likely to cause a fire in the boat? As I say I have a simple effective system but haven't had the time to do destructive testing. Any thoughts on the matter are greatly appreciated.
best wishes Tim
In discussion with jbkiwi, we felt it would be a good idea to bring together into one post the different smoker experiments we have each conducted to make them easier to find for anyone interested in having a go. Here is a summary of my experiments. JB will add his in time.
My implementation is based on an e-cig H2 atomizer. These are readily available at low cost. The unit as purchased comprises a 2ml tank, heating coil, and a coupling which would normally connect to the e-cig electronics/battery. I made a simple end cap from acrylic which is a push fit into the coupling. Any insulating material could be used for this, even a piece of hardwood could be carved to shape. The end cap is held in place with a couple of small screws through the side of the coupling. Before fitting, it was smeared with silicone sealant to ensure an airtight seal. A central screw in the endcap can be adjusted to make electrical contact with the coil. The other contact to the coil is via the body of the coupling, using one of the endcap retaining screws. A brass tube fitted through the side of the endcap allows air to be pushed through the atomizer.
For installation in my Crash Tender, I increased the capacity of the smoke fluid tank by adding an additional tank around the outside of the original atomizer tank. The smoker fluid I use is 3:1 glycerine:water.
The coil seems to work best when energised with around 5 watts of power. This can be achieved by using a DC-DC converer to drop the battery voltage to around 3volts. Simple low cost buck converters are available on-line. As an alternative, a PWM electronic circuit can be used to power the coil direct from the battery voltage, provided the power to the coil does not greatly exceed 5w. I found to my cost that feeding 25w of power into the coil (circuit error!) vaporises the coil in the blink of an eye! Fortunately, replacement coils are readily available. The exposed metalwork of the atomizer typically reaches a temperature of 30 -35C while it is running but that depends on how much power you feed into it.😉
The air pump is not critical. I have tried a couple of different types and the both work well. It is useful to be able to adjust the pump speed, and hence the volume of air being pushed through the atomizer. Small motor speed controllers are easily obtainable.
The atomizer works best mounted in a horizontal position. if mounted vertically, as shown in part of the video, it has a tendancy to flood the coil.
By adjusting the pump speed and the coil power a range of different effects are possible. The video shows several examples of different settings. It is possible to generate just a gentle waft of smoke suitable for a funnel on a tug or a quick pulse of thick smoke possibly suitable to simulate gunfire on a destroyer.
For my Crash Tender I mix pulsed smoke with water using a venturi type connector and then feed the resulting mix out through the exhaust ports. More details of the installation in the Crash Tender can be found in my Crash Tender Refit blog.
Happy to try an answer any questions.
Graham93
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In discussion with jbkiwi, we felt it would be a good idea to bring together into one post the different smoker experiments we have each conducted to make them easier to find for anyone interested in having a go. Here is a summary of my experiments. JB will add his in time.
My implementation is based on an e-cig H2 atomizer. These are readily available at low cost. The unit as purchased comprises a 2ml tank, heating coil, and a coupling which would normally connect to the e-cig electronics/battery. I made a simple end cap from acrylic which is a push fit into the coupling. Any insulating material could be used for this, even a piece of hardwood could be carved to shape. The end cap is held in place with a couple of small screws through the side of the coupling. Before fitting, it was smeared with silicone sealant to ensure an airtight seal. A central screw in the endcap can be adjusted to make electrical contact with the coil. The other contact to the coil is via the body of the coupling, using one of the endcap retaining screws. A brass tube fitted through the side of the endcap allows air to be pushed through the atomizer.
For installation in my Crash Tender, I increased the capacity of the smoke fluid tank by adding an additional tank around the outside of the original atomizer tank. The smoker fluid I use is 3:1 glycerine:water.
The coil seems to work best when energised with around 5 watts of power. This can be achieved by using a DC-DC converer to drop the battery voltage to around 3volts. Simple low cost buck converters are available on-line. As an alternative, a PWM electronic circuit can be used to power the coil direct from the battery voltage, provided the power to the coil does not greatly exceed 5w. I found to my cost that feeding 25w of power into the coil (circuit error!) vaporises the coil in the blink of an eye! Fortunately, replacement coils are readily available. The exposed metalwork of the atomizer typically reaches a temperature of 30 -35C while it is running but that depends on how much power you feed into it.😉
The air pump is not critical. I have tried a couple of different types and the both work well. It is useful to be able to adjust the pump speed, and hence the volume of air being pushed through the atomizer. Small motor speed controllers are easily obtainable.
The atomizer works best mounted in a horizontal position. if mounted vertically, as shown in part of the video, it has a tendancy to flood the coil.
By adjusting the pump speed and the coil power a range of different effects are possible. The video shows several examples of different settings. It is possible to generate just a gentle waft of smoke suitable for a funnel on a tug or a quick pulse of thick smoke possibly suitable to simulate gunfire on a destroyer.
For my Crash Tender I mix pulsed smoke with water using a venturi type connector and then feed the resulting mix out through the exhaust ports. More details of the installation in the Crash Tender can be found in my Crash Tender Refit blog.
