Today's Message Index:
----------------------
1. 02:17 AM - Re: 300mA AA NiMh charger design needed (rparigoris)
2. 04:39 AM - Re: Re: 300mA AA NiMh charger design needed (Robert L. Nuckolls, III)
3. 09:05 AM - Re: Tachometer Generator Wiring (user9253)
4. 09:26 AM - Re: Re: Tachometer Generator Wiring (Andrew Zachar)
5. 09:47 AM - Re: Re: Tachometer Generator Wiring (Bob McCallum)
6. 10:39 AM - Re: Tachometer Generator Wiring (user9253)
7. 11:05 AM - Short in E-Bus Feed Circuit? (jvolkober)
8. 11:40 AM - Re: Re: Tachometer Generator Wiring (Gerry van Dyk)
9. 03:05 PM - Re: Tachometer Generator Wiring (user9253)
10. 07:46 PM - Re: Re: Tachometer Generator Wiring (Robert L. Nuckolls, III)
11. 08:41 PM - Re: 300mA AA NiMh charger design needed (Richard E. Tasker)
Message 1
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| Subject: | Re: 300mA AA NiMh charger design needed |
Hi Bob
Thx. for the reply.
** First off if you don't mind I can send you some AA NiMh cells to test once they
arrive. How many would you like for testing?
** I like the simplicity of the circuit you pointed me to. The first question is
would Allied part number 248-0718 LM317P be OK to use? This is not a National
Semiconductor part, I like the TO220 style and didn't see one offered by National.
** Instead of a LM317, would Allied 288-0963 LM1117T-ADJ Low dropout be an OK choice
with only a 1.2 volt drop out? This should allow a cell count increase?
** You mention that putting cells in a PVC plastic pipe may not be a good idea
because it can aid in heat build up. You mention that this charger will heat the
cells. I am questioning this because in my past experience charging NiMh cells
at a one tenth capacity rate for 14 to 16 hours doesn't seem to develop too
much heat. Has your experience proved in the past that a 1/10C charge rate for
14 to 16 hours warms up the cells? The cells are AA with a 3,000mA capacity,
so 300mAs is 1/10 capacity.
** I would love for this simple circuit to accomplish the task of providing a constant
300mA charge rate. I don't have too much experience working with LM317s.
I can kind of see where if you have a constant supply voltage and a constant
load how the circuit should be OK. In my application where the supply voltage
may be as low as 12.2 volts, or if the motor is running then up to 14.5 volts
do you think it will still maintain a constant 300mAs?
Also we know that when NiMh cells when discharged have a lower resistance. As the
cells begin to charge, the resistance begins to go up thus you need to begin
increasing the voltage in order to maintain a constant 300ma charge rate. Then
when the cells become fully charged the resistance begins to go down again,
thus you need to begin lowering the voltage to maintain a constant current. If
you put too much current into a fully charged cell this is where you can get
them warm or downright hot (IE 1C or more).
Anyway do you think this circuit could do an OK job of maintaining 300mA charge
rate with input voltage fluctuating between 12.2 and 14.5 volts, and the NiMh
cells changing their internal resistance?
** I kinda had an eyeball on this circuit #2:
http://talkingelectronics.com/projects/ChargingNiMH/ChargingNiMH.html
But they are using a constant current 500mA charger that is kinda regulated (because
of transformer coupling?) and wasn't sure how it would work with a source
that could provide a gazillion mAs of current.
I was thinking of trying both the regulators I mentioned above and since Allied
doesn't sell BC338 NPN transistors (Digikey BC338ND), I was thinking of giving
a Allied TIP122G 568-0402 a try. I would rather keep it simple, but if just
the regulator and resistor proves unacceptable results, do you think this would
work OK?
Thx.
Ron Parigoris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=353497#353497
Message 2
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| Subject: | Re: 300mA AA NiMh charger design needed |
At 04:13 AM 9/29/2011, you wrote:
<rparigor@suffolk.lib.ny.us>
Hi Bob
Thx. for the reply.
** First off if you don't mind I can send you some AA NiMh cells to
test once they arrive. How many would you like for testing?
Four. No hurry, that fixture is packed away
somewhere from the move. I'll have to dig it
out and dust it off. I've been thinking about
repeating some of the tests done earlier and
adding a few more 'house brands' of AA-alkalines
to the study. But I'm up to my eyeballs in a
project for Hawker-Beech and it will be a
couple months before I can 'play'.
** I like the simplicity of the circuit you pointed me to. The first
question is would Allied part number 248-0718 LM317P be OK to use?
This is not a National Semiconductor part, I like the TO220 style and
didn't see one offered by National.
** Instead of a LM317, would Allied 288-0963 LM1117T-ADJ Low dropout
be an OK choice with only a 1.2 volt drop out? This should allow a
cell count increase?
ANY of the 117/217/317 series parts will do.
You just need to make sure it's heat-sinked
well enough to dissipate the power. The low
dropout part is only a portion of the voltage
drop . . . the 39 ohm resistor has 1.25 volts
across it too which boosts your head-room
requirements.
** You mention that putting cells in a PVC plastic pipe may not be a
good idea because it can aid in heat build up. You mention that this
charger will heat the cells. I am questioning this because in my past
experience charging NiMh cells at a one tenth capacity rate for 14 to
16 hours doesn't seem to develop too much heat. Has your experience
proved in the past that a 1/10C charge rate for 14 to 16 hours warms
up the cells? The cells are AA with a 3,000mA capacity, so 300mAs is
1/10 capacity.
'Too much heat' is non-quantified. Further,
small surface area parts wrapped in an
low heat transfer media will experience
a greater temperature rise than when
operated in still air. Just a point to
ponder and explore.
** I would love for this simple circuit to accomplish the task of
providing a constant 300mA charge rate. I don't have too much
experience working with LM317s. I can kind of see where if you have a
constant supply voltage and a constant load how the circuit should be
OK. In my application where the supply voltage may be as low as 12.2
volts, or if the motor is running then up to 14.5 volts do you think
it will still maintain a constant 300mAs?
The LMx17 series devices are a fixed calibration
voltage regulator with a factory adjustment of
1.25 volts. Higher voltages can be achieved by
addition of the voltage divider shown in the
data sheets. But when wired with the single resistor
as suggested, the device works to maintain a
constant voltage of 1.25 volts across the series
resistor. 1.25 ohms yields 1 amp, 125 ohms yields
10 milliamps, etc. So yes, this is a true constant
current generator with an upper limit equal to the
design point. It will fall off only if the device
looses operating head-room discussed above.
Also we know that when NiMh cells when discharged have a lower
resistance. As the cells begin to charge, the resistance begins to go
up thus you need to begin increasing the voltage in order to maintain
a constant 300ma charge rate. Then when the cells become fully
charged the resistance begins to go down again, thus you need to
begin lowering the voltage to maintain a constant current. If you put
too much current into a fully charged cell this is where you can get
them warm or downright hot (IE 1C or more).
Anyway do you think this circuit could do an OK job of maintaining
300mA charge rate with input voltage fluctuating between 12.2 and
14.5 volts, and the NiMh cells changing their internal resistance?
Absolutely.
** I kinda had an eyeball on this circuit #2:
http://talkingelectronics.com/projects/ChargingNiMH/ChargingNiMH.html
But they are using a constant current 500mA charger that is kinda
regulated (because of transformer coupling?) and wasn't sure how it
would work with a source that could provide a gazillion mAs of current.
The circuit depicted are variations on a theme and
all will probably function as advertised.
I was thinking of trying both the regulators I mentioned above and
since Allied doesn't sell BC338 NPN transistors (Digikey BC338ND), I
was thinking of giving a Allied TIP122G 568-0402 a try. I would
rather keep it simple, but if just the regulator and resistor proves
unacceptable results, do you think this would work OK?
Yes. The transistor style is not critical. Go get
an LM317 and TIP31 at Radio Shack and do the
experiments.
LM317
http://www.radioshack.com/product/index.jsp?productId 62601&numProdsPerPage=60
TIP31
http://www.radioshack.com/product/index.jsp?productId 62610&numProdsPerPage=60
This is the simplest approach. If you want something
'fancier' with lower heat dissipation, some sort
of active constant current generator like the LED
drivers we offer
https://matronics.com/aeroelectric/Catalog/AEC/9051/9051-700A.pdf
can be used. With a single resistor to adjust
output current, you can set your charging level
at any value up to 1000 mA. Further, this particular
device has a boost output capability. I think it would
charge a longer string of cells.
Bob . . .
Message 3
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| Subject: | Re: Tachometer Generator Wiring |
To Bob and All,
At my age, I know it is only a matter of time before I forget to latch the canopy
before takeoff on a hot sunny day. I have learned from the mistakes of others
and will fly the plane and latch the canopy after landing. But I would rather
not forget to latch the canopy. I want to install an audio and visual alarm
that will only go off when the canopy is unlatched AND the engine is at takeoff
RPM. The easy part of the project will be installing a limit switch on
the canopy latch. My plan is to use a PIC12F509 microprocessor that will monitor
the limit switch and also count the engine RPM. There is a tachometer coil
on the engine that sends an AC signal to the Dynon D-180 through a 30K resistor.
I want to tap into that signal for my project but am worried about loading
down the circuit and affecting the Dynon tach readout. My first question is,
can the tach signal be fed directly into a microprocessor input or should I
use some type of buffer? If a buffer circuit is needed, can I use Bob's transistor
squaring circuit above or will it load down the circuit to the Dynon?
I found this circuit on the internet: http://www.redcircuits.com//Page17.htm
If I used that circuit, I would eliminate the voltage doubler components (C1, C2,
D1, D2) and power the Hex Inverter from a separate supply. Using an op-amp
or FET are possibilities if I could find a schematic. I am open to any comments
or suggestions.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=353522#353522
Message 4
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| Subject: | Re: Tachometer Generator Wiring |
What about using a second limit switch hooked up to your throttle
lever/knob?
That might be simpler...
On Thu, Sep 29, 2011 at 12:01 PM, user9253 <fran4sew@banyanol.com> wrote:
> >
>
> To Bob and All,
> At my age, I know it is only a matter of time before I forget to latch the
> canopy before takeoff on a hot sunny day. I have learned from the mistakes
> of others and will fly the plane and latch the canopy after landing. But I
> would rather not forget to latch the canopy. I want to install an audio and
> visual alarm that will only go off when the canopy is unlatched AND the
> engine is at takeoff RPM. The easy part of the project will be installing a
> limit switch on the canopy latch. My plan is to use a PIC12F509
> microprocessor that will monitor the limit switch and also count the engine
> RPM. There is a tachometer coil on the engine that sends an AC signal to
> the Dynon D-180 through a 30K resistor. I want to tap into that signal for
> my project but am worried about loading down the circuit and affecting the
> Dynon tach readout. My first question is, can the tach signal be fed
> directly into a microprocessor input or should I use some type of buffer?
> If a buffer circuit is ne!
> eded, can I use Bob's transistor squaring circuit above or will it load
> down the circuit to the Dynon?
> I found this circuit on the internet:
> http://www.redcircuits.com//Page17.htm
> If I used that circuit, I would eliminate the voltage doubler components
> (C1, C2, D1, D2) and power the Hex Inverter from a separate supply. Using
> an op-amp or FET are possibilities if I could find a schematic. I am open
> to any comments or suggestions.
> Joe
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=353522#353522
>
>
--
Andrew Zachar
andrew.d.zachar@gmail.com
Message 5
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| Subject: | Re: Tachometer Generator Wiring |
Joe=3B
Another simple solution would be a second limit switch in series with the o
ne on the latch attached to the throttle in such a way that at takeoff powe
r setting it closes and if the one on the latch is also closed (latch open)
then the alarms sound.
Bob McC
> Subject: AeroElectric-List: Re: Tachometer Generator Wiring
> From: fran4sew@banyanol.com
> Date: Thu=2C 29 Sep 2011 09:01:29 -0700
> To: aeroelectric-list@matronics.com
>
m>
>
> To Bob and All=2C
> At my age=2C I know it is only a matter of time before I forget to latch
the canopy before takeoff on a hot sunny day. I have learned from the mist
akes of others and will fly the plane and latch the canopy after landing.
But I would rather not forget to latch the canopy. I want to install an au
dio and visual alarm that will only go off when the canopy is unlatched AND
the engine is at takeoff RPM. The easy part of the project will be instal
ling a limit switch on the canopy latch. My plan is to use a PIC12F509 mic
roprocessor that will monitor the limit switch and also count the engine RP
M. There is a tachometer coil on the engine that sends an AC signal to the
Dynon D-180 through a 30K resistor. I want to tap into that signal for my
project but am worried about loading down the circuit and affecting the Dy
non tach readout. My first question is=2C can the tach signal be fed direc
tly into a microprocessor input or should I use some type of buffer? If a
buffer circuit is ne!
> eded=2C can I use Bob's transistor squaring circuit above or will it loa
d down the circuit to the Dynon?
> I found this circuit on the internet: http://www.redcircuits.com//Page
17.htm
> If I used that circuit=2C I would eliminate the voltage doubler component
s (C1=2C C2=2C D1=2C D2) and power the Hex Inverter from a separate supply
. Using an op-amp or FET are possibilities if I could find a schematic. I
am open to any comments or suggestions.
> Joe
>
> --------
> Joe Gores
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=353522#353522
>
>
>
>
>
>
>
===========
===========
===========
===========
>
>
>
Message 6
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| Subject: | Re: Tachometer Generator Wiring |
Thanks Bob McC & Andrew for the throttle switch ideas. Trouble is, I can not think
of any way to install a switch on the throttle knob. There is a knurled
locking disk in the way. I could install a limit switch on the other end of the
throttle linkage at the carburetor. But that will require fabricating some
type of bracket to hold the switch and figuring out how to mount it to the engine
without interfering with the throttle operation. And the wiring and switch
will be subject to heat and vibration. I would rather monitor the RPM electronically
because making electronic circuits is fun for me.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=353531#353531
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| Subject: | Short in E-Bus Feed Circuit? |
Situation - I am using Z-12. I have a diode, which tests ok, between the main
buss and the e-buss. I have the e-bus wired to a switch and then to the battery
bus per the diagram. For the wire from the e-bus to the switch, with the switch
in the off position, I detect no short to ground. Same for the wire from
the switch to the e-bus. With the switch on I blow the fuse (10amps fuse with
no load on the e-bus). If I detach the wire from the e-bus to the diode between
the e-buss and the main bus, the fuse remains intact. It appears that the
problem is with this circuit, yet the diode tests ok. What am I missing?
(All wiring has been triple checked to conforms with z-12.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=353533#353533
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| Subject: | Re: Tachometer Generator Wiring |
Joe, just a thought...
How about having the canopy warning come on at run-up RPM rather than
take-off RPM. I'd think it'd be best to pick this up before taking the
runway.
Gerry
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of user9253
Sent: September 29, 2011 10:01 AM
Subject: AeroElectric-List: Re: Tachometer Generator Wiring
To Bob and All,
At my age, I know it is only a matter of time before I forget to latch the
canopy before takeoff on a hot sunny day. I have learned from the mistakes
of others and will fly the plane and latch the canopy after landing. But I
would rather not forget to latch the canopy. I want to install an audio and
visual alarm that will only go off when the canopy is unlatched AND the
engine is at takeoff RPM. The easy part of the project will be installing a
limit switch on the canopy latch. My plan is to use a PIC12F509
microprocessor that will monitor the limit switch and also count the engine
RPM. There is a tachometer coil on the engine that sends an AC signal to
the Dynon D-180 through a 30K resistor. I want to tap into that signal for
my project but am worried about loading down the circuit and affecting the
Dynon tach readout. My first question is, can the tach signal be fed
directly into a microprocessor input or should I use some type of buffer?
If a buffer circuit is ne!
eded, can I use Bob's transistor squaring circuit above or will it load
down the circuit to the Dynon?
I found this circuit on the internet:
http://www.redcircuits.com//Page17.htm
If I used that circuit, I would eliminate the voltage doubler components
(C1, C2, D1, D2) and power the Hex Inverter from a separate supply. Using
an op-amp or FET are possibilities if I could find a schematic. I am open
to any comments or suggestions.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=353522#353522
Message 9
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| Subject: | Re: Tachometer Generator Wiring |
> How about having the canopy warning come on at run-up RPM rather than
> take-off RPM.
Gerry,
That is a good idea. I could get into the habit of latching the canopy before
run-up. In the event that the takeoff is delayed and I unlatch the canopy, the
alarm will still go off on the takeoff roll, but at a lower RPM.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=353560#353560
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| Subject: | Re: Tachometer Generator Wiring |
At 11:01 AM 9/29/2011, you wrote:
>
>To Bob and All,
>At my age, I know it is only a matter of time before I forget to
>latch the canopy before takeoff on a hot sunny day.My plan is to use
>a PIC12F509 microprocessor that will monitor the limit switch and
>also count the engine RPM.
Is this a Dynon sensor? Call the factory and see
what the characteristics of this signal are. It
may already be a 5 or 12v square wave. If so,
you can tie it to a PIC input through a suitable
series resistor, a capacitor and perhaps a clamp diode.
Use one of edge sensitive inputs. But the first
question to answer is what does the signal look
like? If you can run the engine now, the a 'scope
would get you this information too.
I have a little "do everything" board and enclosure
that might be suited to your task. See:
http://aeroelectric.com/Pictures/Schematics/Do-Much_Board.pdf
http://www.aeroelectric.com/Catalog/AEC/9011/A15_Package.jpg
Depending on what parts are installed on the board, what
parts are left off, and what code goes into the
8-pin PIC, you can do a whole lot of neat things.
Bob . . .
Message 11
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| Subject: | Re: 300mA AA NiMh charger design needed |
Bob, your calculations are off by a factor of ten relative to the resistor needed
to get 300 mA.
The 317 series has a reference voltage of 1.25V as you noted. But to get 300 mA
you would need 1.25V/0.3A = 4.17ohms. A value of 3.9 ohms is the closest 5%
resistor value and it would give you 320
mA - likely close enough. You would need at least a 1/2 W resistor for this application
and a 1W would keep the temperature rise in the resistor more reasonable.
Other than that everything else you say is fine.
It should be noted that using a charger like this is fine as long as one removes
it shortly after the batteries are fully charged. Otherwise, the overcharging
will shorten their useful lives.
Dick Tasker
Robert L. Nuckolls, III wrote:
>
> At 03:10 PM 9/28/2011, you wrote:
>>
>> Hi Group
>>
>> I need a design for an easy to build, low parts count and inexpensive constant
current circuit to charge 3,000mA AA NiMh batteries (~300mA rate C/10 for 14
to 16 hours) from a 12 volt lead acid
>> battery that could have the input voltage ranging anywhere from ~ 12.2 to 14.5volts.
>>
>> I would prefer to have as many cells in series as possible when charging.
>
> The simplest is an LM317 wired as shown here
>
> http://diyparadise.com/yhlmccs.html
>
> The resistor would be 1.25/.3 or 39 ohms.
> The CC Gen will need at least 3 volts
> of 'headroom' so 12.5 - 3.0 leaves
> 9.5 volts worth of cells. This means
> you can charge 6 cells in series.
>
> This charge rate will heat the cells.
> Plastic pipe may not be the best holder
> for allowing the string of cells to
> reject heat.
>
> If you like, I could take a few of those
> cells and discharge them on the system I
> used to produce this article:
>
> http://aeroelectric.com/articles/AA_Bat_Test.pdf
>
>
> Bob . . .
>
>
--
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