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Home > Archive > Alternative Power sources > September 2007 > miniature generator
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miniature generator
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| rip_t@hotmail.com 2007-09-14, 9:25 am |
| ive been building a minature genorator based on a small rc car engine
and have almost finished, but before i start it up poroperly i have a
couple of questions that worry me
the engine is rather basic and has no govenor. but the load on the
genorator will always be a switch mode power supply (either 15 in
energiser nimh battery chargers which ive opend up and am pretty sure
a smps or a laptop 12v car power supply.
so how can i match the engine power to the load needed. becasue when
charging the load will be 120w yet at full throttel the engine can put
out 200-300w. my fear is that the speed will rise and so will voltage
until it become too great for the smps to handel. is their any risk
and how can i match the load, either for fear of damagign equipment or
to save on fuel?
incase it makes a ny diffrence im using a brushless plane motor so
effectivly a 3 phase motor which i rectife. how can these things be
so powerful in such a small space for =A320 i got a 1kw motor that is
about as big as a walnut. howcome i dont see these things and the also
teeny pwm speed controllers being used for other projects ect
any help would be greatly appreciated
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| Ken Maltby 2007-09-14, 1:25 pm |
|
<rip_t@hotmail.com> wrote in message
news:1189768545.670470.205950@y42g2000hsy.googlegroups.com...
ive been building a minature genorator based on a small rc car engine
and have almost finished, but before i start it up poroperly i have a
couple of questions that worry me
the engine is rather basic and has no govenor. but the load on the
genorator will always be a switch mode power supply (either 15 in
energiser nimh battery chargers which ive opend up and am pretty sure
a smps or a laptop 12v car power supply.
so how can i match the engine power to the load needed. becasue when
charging the load will be 120w yet at full throttel the engine can put
out 200-300w. my fear is that the speed will rise and so will voltage
until it become too great for the smps to handel. is their any risk
and how can i match the load, either for fear of damagign equipment or
to save on fuel?
incase it makes a ny diffrence im using a brushless plane motor so
effectivly a 3 phase motor which i rectife. how can these things be
so powerful in such a small space for £20 i got a 1kw motor that is
about as big as a walnut. howcome i dont see these things and the also
teeny pwm speed controllers being used for other projects ect
any help would be greatly appreciated
I would think that an RC car engine would have some
simple preportional servo accuated throtle controls. You
should be able to modify them to respond to your generator's
output instead of a radio receiver. You might even have it
able to respond based on the battery level, for the charger.
Just a first impression, from your general description.
Luck;
Ken
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| Arnold Walker 2007-09-14, 1:25 pm |
|
<rip_t@hotmail.com> wrote in message
news:1189768545.670470.205950@y42g2000hsy.googlegroups.com...
ive been building a minature genorator based on a small rc car engine
and have almost finished, but before i start it up poroperly i have a
couple of questions that worry me
the engine is rather basic and has no govenor. but the load on the
genorator will always be a switch mode power supply (either 15 in
energiser nimh battery chargers which ive opend up and am pretty sure
a smps or a laptop 12v car power supply.
so how can i match the engine power to the load needed. becasue when
charging the load will be 120w yet at full throttel the engine can put
out 200-300w. my fear is that the speed will rise and so will voltage
until it become too great for the smps to handel. is their any risk
and how can i match the load, either for fear of damagign equipment or
to save on fuel?
incase it makes a ny diffrence im using a brushless plane motor so
effectivly a 3 phase motor which i rectife. how can these things be
so powerful in such a small space for £20 i got a 1kw motor that is
about as big as a walnut. howcome i dont see these things and the also
teeny pwm speed controllers being used for other projects ect
any help would be greatly appreciated
Sounds like you want a governor like on a arc welder.
A combination of droop with a idle switch.
You can see both mechical control like on the old welders and electronic
control like on the new welders.
no load it goes to idle....strike an arc it goes to constant velicity with a
droop control like on tractor or a standard generator.
You looked at a helicopter RC engine control since at least on the full
size and drone turbine helicopters engines, you are running constant
velicity with a droop.There is also an idle position.I would think the RC
engine would be straight electronic like on the arc welder more so than
the complex system used on turbines(They are a combination of electronic
/hydro-pnuematic.Because of all the stuff beyond speed control that
you are needing......acceleration ,pressure,etc. Like an old Woodard control
used on both steam and gas turbines.)
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| |
|
| Small engines are usually less efficient than bigger for some reason
or another... otherwise I guess we'd have lots of small engines in
ships instead of one ot two big ones. Anyway, I think you should get a
4 stroke model airplane engine, which should have better specific fuel
consumption than a 2 cycle of the same displacement, and set it up on
a bench with a fuel flow meter and an alternator with a rheostat on
the field coil, and find the 'sweet spot' in the rpm and alternator
load setting that minimizes fuel consumption. Once you know this exact
volts and amps in the alternator, you can get a BLDC kit and put on a
custom winding to match that exact setting. If the load varied more or
less than this tuned setting, the effciency would drop on either
side... careful measurement would show if the power used to excite the
field coils in the alternator (a dozen watts?) could be tolerated in
order to gain the advantage of matching a varying electrical (and thus
mechanical) load. Since I'm a programmer, I think this would be a
great job for a $5 microcontroller, but you might be able to find a
nice young man from Shanghai that would adjust the knob whenever the
generator was running for whatever the prevailing wage is over there.
Couple bucks a day?
| |
| Neon John 2007-09-15, 9:25 am |
| On Fri, 14 Sep 2007 04:15:45 -0700, rip_t@hotmail.com wrote:
>ive been building a minature genorator based on a small rc car engine
>and have almost finished, but before i start it up poroperly i have a
>couple of questions that worry me
>
>the engine is rather basic and has no govenor. but the load on the
>genorator will always be a switch mode power supply (either 15 in
>energiser nimh battery chargers which ive opend up and am pretty sure
>a smps or a laptop 12v car power supply.
>
>so how can i match the engine power to the load needed. becasue when
>charging the load will be 120w yet at full throttel the engine can put
>out 200-300w. my fear is that the speed will rise and so will voltage
>until it become too great for the smps to handel. is their any risk
>and how can i match the load, either for fear of damagign equipment or
>to save on fuel?
Man, I hope your construction techniques are better than your spelling and grammar!
This little generator
http://www.neon-john.com/Generator/generator.jpg
is of about the same architecture as you describe - a fixed throttle engine (see the
throttle setting nut on top of the carburetor) attached to a 3 phase permanent magnet
alternator driving a 60 hz inverter.
Speed control is effected by an ignition cutout rev limiter built into the electronic
control box. This thing cuts ignition sparks in a random fashion to hold the speed
constant.
The general procedure is this. Start the engine and rev it up using the manual
throttle nut to a point where it will accept load and the green light flickers. Apply
the load. Reduce the engine speed until the green light comes on solid, then
increase it until the light flickers. The flicker shows the operation of the rev
limiter.
If your engine is glow plug based then your easiest option is to replace the glow
plug with a spark plug and implement a similar scheme. Barring that, about your only
other reliable and efficient option is to connect up an R/C servo to the throttle and
drive it with some electronics that look at engine speed or alternator output. A
BASIC Stamp or PIC processor will do the job nicely. You could probably do it in the
analog domain with a dual 556 timer chip but the digital method would be so much
simpler and reliable.
If fuel efficiency isn't a major issue then you could design a variable energy dump
into your controller. Energy not used by the load is shunted to a dummy load
resistor, maintaining a constant load on the engine. This control scheme is
frequently used on micro-hydro electric plants where the "fuel" is free. Perhaps the
fuel penalty won't be too severe if you advance the throttle only enough to handle
the beginning of the charge cycle and then let the energy dump handle things as the
battery charges.
My preferred approach would be the servo/microprocessor route.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
What do you call 4 Blondes in an Abrams? Air Tank.
| |
| rip_t@hotmail.com 2007-09-15, 9:25 am |
| On 15 Sep, 10:26, Neon John <n...@never.com> wrote:
> On Fri, 14 Sep 2007 04:15:45 -0700, ri...@hotmail.com wrote:
>
>
>
> Man, I hope your construction techniques are better than your spelling and grammar!
>
> This little generator
>
> http://www.neon-john.com/Generator/generator.jpg
>
> is of about the same architecture as you describe - a fixed throttle engine (see the
> throttle setting nut on top of the carburetor) attached to a 3 phase permanent magnet
> alternator driving a 60 hz inverter.
>
> Speed control is effected by an ignition cutout rev limiter built into the electronic
> control box. This thing cuts ignition sparks in a random fashion to hold the speed
> constant.
>
> The general procedure is this. Start the engine and rev it up using the manual
> throttle nut to a point where it will accept load and the green light flickers. Apply
> the load. Reduce the engine speed until the green light comes on solid, then
> increase it until the light flickers. The flicker shows the operation of the rev
> limiter.
>
> If your engine is glow plug based then your easiest option is to replace the glow
> plug with a spark plug and implement a similar scheme. Barring that, about your only
> other reliable and efficient option is to connect up an R/C servo to the throttle and
> drive it with some electronics that look at engine speed or alternator output. A
> BASIC Stamp or PIC processor will do the job nicely. You could probably do it in the
> analog domain with a dual 556 timer chip but the digital method would be so much
> simpler and reliable.
>
> If fuel efficiency isn't a major issue then you could design a variable energy dump
> into your controller. Energy not used by the load is shunted to a dummy load
> resistor, maintaining a constant load on the engine. This control scheme is
> frequently used on micro-hydro electric plants where the "fuel" is free. Perhaps the
> fuel penalty won't be too severe if you advance the throttle only enough to handle
> the beginning of the charge cycle and then let the energy dump handle things as the
> battery charges.
>
> My preferred approach would be the servo/microprocessor route.
>
> John
> --
> John De Armond
> See my website for my current email addresshttp://www.neon-john.comhttp://www.johndearmond.com<-- best little blog on the net!
> Tellico Plains, Occupied TN
> What do you call 4 Blondes in an Abrams? Air Tank.
thank for all the input
my hope was to try and avoid too much electronics but it might not be
avoidable and the servo and micro controller looks like the best bet
the engine is rated at 4,000 to 28,000 rpm and the motor is 833 rpm
per volt. and considering im turning the 3 phase ac into dc i dont
mind what the frequency is, and as i can pass all the power through a
smps that means i don't really mind what the voltage is as i can have
an input of 8-35 v absolute limits and use the smps to turn it into
any voltage i want and even at the highest rpm for the engine that
only leads to an input voltage of 33 v
also the battery charge has the smps built in and it seems to work by
dumping discrete chunks of energy into the battery then determining
whether it needs another, meaning the charge uses its full rated power
for almost the entire charging cycle (it goes a bit strange at the
last portion)
could i then get away with manually setting the throttle down to where
it sounds like its struggling to power the charger (close to stalling)
then push up a bit it should be roughly balanced. the charge has a
indicator to show it has finished and i could connect it to a relay to
shut off the engine. does this sound fairly efficient or do i have to
bite the bullet and finally learn more about micro controllers
seeing as i wanted to make this generator so that i could have power
for a laptop while camping in more remote areas charging the battery
pack which is 96wh in 48 minutes then i can use the laptop for nearly
5 hours as its 20 w. so it would not be too much extra fuss to
manually tune if i wanted to connect it to any other load as long as
its relatively constant
| |
| Anthony Matonak 2007-09-15, 1:25 pm |
| rip_t@hotmail.com wrote:
....
> seeing as i wanted to make this generator so that i could have power
> for a laptop while camping in more remote areas charging the battery
> pack which is 96wh in 48 minutes then i can use the laptop for nearly
> 5 hours as its 20 w. so it would not be too much extra fuss to
> manually tune if i wanted to connect it to any other load as long as
> its relatively constant
I know this is not what you're asking about but have you considered
a solar PV panel? They're probably more expensive than what you're
discussing but there is less to go wrong, no fuel requirement and
they don't make noise.
For example...
SUNLINQ FOLDING MODULE Solar Panels (12 Watt) $169
http://solarhome.org/index.asp?Page...ROD&ProdID=1134
Sunlinq 25 watt Folding Solar Power Panel $399
http://www.21st-century-solar.com/PROD/GSE25
Folding 48 Watt Solar PV Panel from Global Solar $859
http://solardyne.stores.yahoo.net/fol48watsolp.html
Anthony
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| Vaughn Simon 2007-09-17, 8:25 pm |
|
"Jim" <jim@home.con> wrote in message
news:n4EHi.2847$4J3.1122@newssvr22.news.prodigy.net...
> This strikes me as still quite high....
> Whatever became of the amorphous PV cells we heard about years ago??????
The new "cheap but high efficiency" cells are always due next year.
(Let's designate that as Murphy's fourth law.)
Vaughn
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"Vaughn Simon" <vaughnsimonHATESSPAM@att.FAKE.net> wrote in message
news:W2FHi.562292$p47.179909@bgtnsc04-news.ops.worldnet.att.net...
>
> "Jim" <jim@home.con> wrote in message
> news:n4EHi.2847$4J3.1122@newssvr22.news.prodigy.net...
>
> The new "cheap but high efficiency" cells are always due next year.
>
> (Let's designate that as Murphy's fourth law.)
Agreed. <eg>
>
> Vaughn
>
>
| |
| Morris Dovey 2007-09-18, 3:25 am |
| Vaughn Simon wrote:
| "Jim" <jim@home.con> wrote in message
| news:n4EHi.2847$4J3.1122@newssvr22.news.prodigy.net...
|| This strikes me as still quite high....
|| Whatever became of the amorphous PV cells we heard about years
|| ago??????
|
| The new "cheap but high efficiency" cells are always due next
| year.
|
| (Let's designate that as Murphy's fourth law.)
Sturgeon's Law:
/Everything/ takes longer and costs more.
....and my favorite recursion:
Before you can do /anything/, there's something else that
has to be done first.
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/
| |
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|
"Morris Dovey" <mrdovey@iedu.com> wrote in message
news:46ef3d81$0$3571$815e3792@news.qwest.net...
> Vaughn Simon wrote:
> | "Jim" <jim@home.con> wrote in message
> | news:n4EHi.2847$4J3.1122@newssvr22.news.prodigy.net...
> || This strikes me as still quite high....
> || Whatever became of the amorphous PV cells we heard about years
> || ago??????
> |
> | The new "cheap but high efficiency" cells are always due next
> | year.
> |
> | (Let's designate that as Murphy's fourth law.)
>
> Sturgeon's Law:
>
> /Everything/ takes longer and costs more.
>
> ...and my favorite recursion:
>
> Before you can do /anything/, there's something else that
> has to be done first.
In our rush to create Murphy's Fourth Law we encounter his First Law.
Something has gone wrong; we were beaten to the punch! LOL!!!
>
> --
> Morris Dovey
> DeSoto Solar
> DeSoto, Iowa USA
> http://www.iedu.com/DeSoto/
>
>
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