---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 09/29/11: 11 ---------------------------------------------------------- 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 _____________________________________ Time: 02:17:28 AM PST US Subject: AeroElectric-List: Re: 300mA AA NiMh charger design needed From: "rparigoris" 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 _____________________________________ Time: 04:39:42 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: 300mA AA NiMh charger design needed At 04:13 AM 9/29/2011, you wrote: 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 _____________________________________ Time: 09:05:09 AM PST US Subject: AeroElectric-List: Re: Tachometer Generator Wiring From: "user9253" 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 _____________________________________ Time: 09:26:50 AM PST US Subject: Re: AeroElectric-List: Re: Tachometer Generator Wiring From: Andrew Zachar 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 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 _____________________________________ Time: 09:47:22 AM PST US From: Bob McCallum Subject: RE: AeroElectric-List: 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 _____________________________________ Time: 10:39:32 AM PST US Subject: AeroElectric-List: Re: Tachometer Generator Wiring From: "user9253" 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 ________________________________ Message 7 _____________________________________ Time: 11:05:20 AM PST US Subject: AeroElectric-List: Short in E-Bus Feed Circuit? From: "jvolkober" 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 ________________________________ Message 8 _____________________________________ Time: 11:40:55 AM PST US From: "Gerry van Dyk" Subject: RE: AeroElectric-List: 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 _____________________________________ Time: 03:05:27 PM PST US Subject: AeroElectric-List: Re: Tachometer Generator Wiring From: "user9253" > 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 ________________________________ Message 10 ____________________________________ Time: 07:46:41 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 ____________________________________ Time: 08:41:44 PM PST US From: "Richard E. Tasker" Subject: Re: AeroElectric-List: 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 . . . > > -- Please Note: No trees were destroyed in the sending of this message. 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