Not a problem. I'd probably pick something like an 470 or 1000 uF electrolytic. Simply connect the capacitor's + terminal to battery + terminal and - to -. This is a simplification but the capacitor will act like a battery. When connected and transistor is off, it will charge up to the battery voltage. When the transistor is turned on, it will discharge through the transistor/igniter. Perhaps a better way to say it is it will help keep the battery voltage from slumping.

 

On a filament bulb, yes, the filament needs to be exposed. In a little experiment, I cut the top from a " Holliday Light" , maybe rated around 3V @ 120 mA, wrapped masking tape around it to make a snug fit into a brass fitting for propane- oxygen cannon, applied current from 3 AA NiMH cells & Bang. Lost a bit of glass but filament still good. If using a bulb I would remove all outer glass. No augmenting with cap. is needed. Cost about $ .60 / pop using a # 123 lamp.

 

Not a problem. I'd probably pick something like an 470 or 1000 uF electrolytic. Simply connect the + capacitor's terminal to + battery terminal and - to -. This is a simplification but the capacitor will act like a battery. When connected and transistor is off, it will charge up to the battery voltage. When the transistor is turned on, it will discharge through the transistor/igniter. Perhaps a better way to say it is it will help keep the battery voltage from slumping.

Very kind, thanks, Philba. I'm going to experiment.

There are many useability and safety reasons why it is better for us to use the Glow Plug vs the rocket ingniters/filament/resistance wire etc, so I have to persist.

Gaetan

 

On a filament bulb, yes, the filament needs to be exposed. In a little experiment, I cut the top from a " Holliday Light" , maybe rated around 3V @ 120 mA, wrapped masking tape around it to make a snug fit into a brass fitting for propane- oxygen cannon, applied current from 3 AA NiMH cells & Bang. Lost a bit of glass but filament still good. If using a bulb I would remove all outer glass. No augmenting with cap. is needed. Cost about $ .60 / pop using a # 123 lamp.

Bernard, thank you again. Seems like you are doing a lot of my actual testing for me!

I am going to source some lamps and do some testing as well. Main thing will be how I can make them safe for other operators to install and use.

LB

 

What you are discovering is there are multiple ways to do something. All have pros and cons. Your job is to sort through them and pick the one that meets your needs. I do think the light bulb filament approach has it's advantages.

 

What you are discovering is there are multiple ways to do something. All have pros and cons. Your job is to sort through them and pick the one that meets your needs. I do think the light bulb filament approach has it's advantages.

Yes, Philba, I too see the advantages of the alternatives to the glow plugs. I'm going to continue testing with multiple ignition methods and let the results show me the best way!

LB

 

I think that part of what is behind b380be's intention in post #3 is that when you put a load on a battery the voltage at the terminals goes down because there is resistance in the battery itself. When you start talking 2.5 amps some of the flashlight cells fall to their knees. In one project I was trying to pull about 2 amps out of a carbon-zinc D cell. I finally got close to that goal but the voltage had dropped to about half. b380be made a specific recommendation, probably representative of the type of cell you should be looking at.

Either of these two On Semiconductor P-channel MOSFETs might be able to do the job if you can get good batteries that can keep the voltage up when the current is drawn. The transistors are in stock Newark/Element 14/ Farnell -guess the name depends on which geographical region you are in.

CPH3350-TL-W
http://www.farnell.com/datasheets/2...5.1566298488.1512026256-1500129595.1509899757

MCH3377-TL-W
http://www.farnell.com/datasheets/2...4.1566298488.1512026256-1500129595.1509899757

Being P-Channel MOSFETs, they are "upside-down" from your NPN bipolar transistor. To use these you would connect the source to battery +, connect the load to the drain, and the other end of the load to ground. The gate would normally be kept at battery + and connected to ground to turn it on.

The weak point in this is still the power source.

If all the ATTINY85 is doing is acting as a two second timer, you can do this with a much less expensive one-shot such as the LMC555C or the NE555. I imagine that with 8kk or flash you can do a lot more than that.

Let me start by saying that I'm not questioning your wisdom - I know you know your stuff. This question is for my own education...

I was under the impression that n-channel mosfets almost always have lower Rds-on for a given size and price. Is there a reason you suggested p-channel mosfets here?

 

It is all coming back to the power, isn't it. Thank you for adding to be80be's advice. I'm fast realising that 2xAA might just be fanciful thinking.

Given that the Glow Plugs only want 1.5 volts (the manufacturers don't warranty them beyond 1.5v), you can imagine how my electronically-uneducated brain thinks 3.0 volts should be more than sufficient. But it is because of the switching role of the transistor...

I think the concern here about your battery choice is more about current than voltage. As you've shown, your controller and your glow plug are all happy with the voltage from two batteries, but two batteries can't consis, reliably deliver the amount of current you need. Batteries have internal resistance. When you're driving a light load (fractions of an amp) the internal resistance of the battery is almost transparent - it doesn't noticeably impact behavior of your circuit.

However, when you ask for 2.5 amps from AA batteries, the internal resistance becomes a significant portion of the circuit, causing voltage to sag.

Maybe the distinction I'm making is irrelevant in this context. Either way, you're pushing your luck with AAs.

 

I think the concern here about your battery choice is more about current than voltage. As you've shown, your controller and your glow plug are all happy with the voltage from two batteries, but two batteries can't consis, reliably deliver the amount of current you need. Batteries have internal resistance. When you're driving a light load (fractions of an amp) the internal resistance of the battery is almost transparent - it doesn't noticeably impact behavior of your circuit.

However, when you ask for 2.5 amps from AA batteries, the internal resistance becomes a significant portion of the circuit, causing voltage to sag.

Maybe the distinction I'm making is irrelevant in this context. Either way, you're pushing your luck with AAs.

Hmm, yes, ebeowulf17, thanks.

I'm just so far out of my depth, and uncertain how this will all be resolved. In the remote control car/plane world, they fire up these glow plugs using a single 1.5v battery. Most often a rechargable, but also an alkaline. Indeed, I can sit here connecting/disconnecting a glow plug to a single AA battery repeatedly and it glows red hot within a second, time and time again.

In our real world application, that glow will be required for 1/2 seconds maybe five times in a day, that's it.

I just haven't yet figured out how to electrically switch the power on to the glow plug. The electrical understanding/data sheets/calculations are still out of my mental reach at my early-stage electronics education!

I just haven't been able to get sufficient amperage through the switch(transistor), that seems to be my stumbling point and I hope the suggestions above will solve that. I'm just trying to find a through-hole alternative to the suggestions.

LB

 

Glow plugs will work with 1.5 volts if it what I'm thinking your using the kind that's in small airplanes like the old cox. You'd start it with a D battery that had a holder that snapped on it.
They took time to get hot. I don't think they pulled 2.5 amps.

The small light bulb would be the way to go remove the glass fix it to pop your balloon.

In your first post you say

heating element to explode the balloon

What gas is in the balloon?

 

Glow plugs will work with 1.5 volts if it what I'm thinking your using the kind that's in small airplanes like the old cox. You'd start it with a D battery that had a holder that snapped on it.
They took time to get hot. I don't think they pulled 2.5 amps.

Yes, be80be, they're the ones. They might pull just under 2 amps. The versions we have tested and are now using glow immediately.

The small light bulb would be the way to go remove the glass fix it to pop your balloon.

It'd likely that this would be used by operators other than ourselves so we wanted to make it as self contained as possible. Also, the glow plug doesn't need replacing so that is another attraction.

What gas is in the balloon?

We just inflate with air. There is also some coloured powder for effect. for safety reasons, no gas. I'm in Australia by the way and our laws are very strict around anything that goes bang.

LB

 

Hmm, yes, ebeowulf17, thanks.

I'm just so far out of my depth, and uncertain how this will all be resolved. In the remote control car/plane world, they fire up these glow plugs using a single 1.5v battery. Most often a rechargable, but also an alkaline. Indeed, I can sit here connecting/disconnecting a glow plug to a single AA battery repeatedly and it glows red hot within a second, time and time again.

In our real world application, that glow will be required for 1/2 seconds maybe five times in a day, that's it.

I just haven't yet figured out how to electrically switch the power on to the glow plug. The electrical understanding/data sheets/calculations are still out of my mental reach at my early-stage electronics education!

LB

Hmm, yes, ebeowulf17, thanks.

I'm just so far out of my depth, and uncertain how this will all be resolved. In the remote control car/plane world, they fire up these glow plugs using a single 1.5v battery. Most often a rechargable, but also an alkaline. Indeed, I can sit here connecting/disconnecting a glow plug to a single AA battery repeatedly and it glows red hot within a second, time and time again.

In our real world application, that glow will be required for 1/2 seconds maybe five times in a day, that's it.

I just haven't yet figured out how to electrically switch the power on to the glow plug. The electrical understanding/data sheets/calculations are still out of my mental reach at my early-stage electronics education!

I just haven't been able to get sufficient amperage through the switch(transistor), that seems to be my stumbling point and I hope the suggestions above will solve that. I'm just trying to find a through-hole alternative to the suggestions.

LB

Rechargeable batteries can deliver much higher current than alkaline ones, so that's a different ballgame. Still, I'm not really in s position to judge alkaline's suitability for your project - if it works, great!

As for the switching problem, I think you've gotten solid advice on mosfets. Using the right mosfet should be nearly the same as using the battery directly with no transistor of any kind.

 

As for the switching problem, I think you've gotten solid advice on mosfets. Using the right mosfet should be nearly the same as using the battery directly with no transistor of any kind.

Your confirmation of the MOSFET advice is appreciated, ebeowulf17.

I'm enroute to pick up some this afternoon to start some more testing.

Thank you.

LB

 

Rechargeable batteries can deliver much higher current than alkaline ones

That depends on what your calling rechargeable
Li/FeS2 primary batteries putout the most but there not rechargeable
NiCd put out the least are rechargeable
In a AA the poster would need NiMH batteries
The 18650e Li-ion 3.7 volt can putout 2.2 amps a AA Li-ion is .8 amps

 

Does the balloon go pop without the power ? Does the golf ball penetrate the balloon ?

 

LB......I would look for a way to explode the balloon with a lot less power consumption. And in a very quick manner. Maybe a compressed spring that can be triggered to drive a pin or blade.

You could always delay the bang...for other effects.....with the ATTiny.

I don't know how you have your balloon tied off....or have it cradled.....but playing with a solenoid air valve....instead of exploding......you might control or restrict air flow.......to set balloon off and up doing curly Qs.

One could add a little helium. Then re-use everything.

 

Does the balloon go pop without the power ? Does the golf ball penetrate the balloon ?

No, Bernard, the balloon doesn't break from the golf ball's impact. Typically we use lightweight, short flight, balls (BirdieBalls) so we can hold events in small areas.

LB

 

LB......I would look for a way to explode the balloon with a lot less power consumption. And in a very quick manner. Maybe a compressed spring that can be triggered to drive a pin or blade.

You could always delay the bang...for other effects.....with the ATTiny.

I don't know how you have your balloon tied off....or have it cradled.....but playing with a solenoid air valve....instead of exploding......you might control or restrict air flow.......to set balloon off and up doing curly Qs.

One could add a little helium. Then re-use everything.

Thanks, BR-549, food for thought. Interestingly I'm not wedded just to the popping, it's just that we got so far down that path that I'd like to see the idea to it's end.

The compressed spring interests me. Originally we had started this whole project with a solenoid pin in mind but that didn't work because the travel distance of the pin was insufficient to overcome the latex' elasticity. The spring idea might be a suitable alternative. Can you think of any devices that might use a similar mechanism?

LB

 

BR-549 has a good idea- called a mouse trap; a small solenoid takes place of the cheese, a blade is attached to swinging arm = slash-bang.

 

I watched your video how was you turning on the glow plug with the uno
relay a 1.5 volt battery. You do realise that when you go from 1.5 to 3 volts the batteries
now need to output 5 amps. if the glow plug is for 2.5 amps at 1.5 volts the loading of the batteries come into play the more you add the less current you'll get.
1 AA is right at the limit of giving you 2.5 amps when you add 1 to get 3 volts the batteries resistance come into play.