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davidl

LoMA:Replace by 12C67X?

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Hugh !

Thank's for your projet.

I do sailplane in France by Mistral (a wind >50 km/h),

with my friends, and we plane a very long time (1 or 2 hours).

It is possible to replace the 12C50X by 12C67X (4 Analog) because

i would know the low batery voltage detection by the piezo (for example).

by advance, thank's

and excuse for my english... :blink:

Davidl

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I suppose you mean 12F675..

That would really be an idea to switch, a flash part has the enormous advantage of not having to worry about programming errors... just erase and reprogram :P

I use this one for all my projects and it really is useful.

Edited by Kilrah

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The Flash parts are great for development or for designs that are subject to change. They can help me as I create the software.

However, I often post designs that use the non-Flash PIC12C50x parts. Because they are cheap and the required programmer can be built for almost nothing. That part is good for the folks that build my stuff.

I considered adding a low voltage feature, but the goal of LoMA was to create the world's simplest lost model alarm. Three parts seems to qualify for that. :) Adding a voltage detection input to the LoMA would be more than just a software & PIC change. You would also need an resistive attenuator and a voltage reference. It no longer would have met my goal.

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Well, the Flash PIC costs $1 more, and the programmer is the same... :huh:

And you don't risk to have to throw away 3 PICs because of programming errors...

Edited by Kilrah

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In case you are an experienced hardware engineer, a low voltage alarm can be added without changing the LoMA software. Just remember that the alert buzzer is triggered whenever the PIC's R/C signal is missing.

Just think about that. The rest is up to you. ;)

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Hugh !

I must cut the RX signal if i want the alert buffer !

How many component ?

a icl8211 ?

Do you have some idea of schematic ?

Thank's

DavidL

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Mr Kilrah, i don't inderstand you about "flash pic" :huh:

These are the PICs with an F in the part number. They have Flash memory that can be erased and reprogrammed many times, as opposed to the C parts that use PROM memory and can be programmed only once.

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Hello

Is it possible, Mr RC-CAM to use the not use PIN3 in Input ?

For example 0V=do nothing 5V=force buzzer ON

I would use this pin for add the low voltage alarm.

By advance thank's.

DavidL

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That pin is currently used. It is an active high going output for driving a transistor buffered alarm. It is for those folks that needed to use a high current buzzer. It is not discussed in the article, but would be once a suitable buzzer was identified.

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OK,

They can't use one of the outpout buzzer for drive the transistor ?

are the three outpout needed to drive the buzzer ?(3*20ma=60ma!)

I can't get one in input...

I don't see the solution for my low voltage alarm...

thank's

DavidL

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The three ganged outputs are open collector active low drive outputs. Designed for sinking the low current buzzer. The undocumented output is TTL active high for sourcing a transistor for high current applications.

As mentioned, you can solve your project without changes to the software. All you have to do is switch/clamp/interrupt the R/C servo signal when you detect low battery voltage. It will require about as much additional hardware as what you are proposing. But, you will have to design it since I don't whip this stuff up without first building it and testing it myself. I just don't have time to do that for every causal request.

Also, it is not practical for me to create customized code for each persons needs. I do adopt the ideas from RC-Cam project builders that I think have broad appeal. If there is sufficient demand for an R/C alarm that has voltage and lost signal detection then I might create it in the future. It would not at all look like the LoMA design and will not be as simple.

If I get some free time I will try to find an interim solution. But, there are many talented members on this forum. Perhaps one of them will create a custom PIC chip for you or will offer a working schematic on how to adapt LoMA for your needs. Or, you can always build the voltage alarm that was shown in the link to rcgroups.com.

Edited by Mr.RC-Cam

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Hugh !

Ok !

Thank's for all.

I search to "switch/clamp/interrupt" the R/C servo signal when low battery voltage detected.

If any body can help me ...

DavidL

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What is the voltage trip point you need? Does it need to be adjustble (if so, what range)? That info will be needed before anyone can provide a specific design.

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Hello !

the voltage trip point need to be adjustble.

4 accus =>4*1.2-0.2=4,6v

5 accus =>5*1.2-0.2=5,8v

2lipo =>2*3.6-0.6=6,6V

3lipo =>3*3.6-0.6=10,2V

X accus =>X * U nominal-DeltaU=U Alarm

DeltaU=U nominal(1accus)-U empty(1accus)

It's my formule... ;)

For beginning the U alarm = 4,6V.

Thank's for you help.

Davidl

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Attached is an example circuit for adding low voltage detection to LoMA. It uses a MAX8211, which can be obtained as free samples from maxim-ic.com

The voltage range is very broad and is adjusted via a pot. It will easily cover the 4.6V to 10.2V range you requested.

If this circuit does not suit your needs, or you do not like the parts used, then just use it as a basis to design something that is better for you. Sure, there are other ways to do this. But, this is all I will present (I do not have time to develop alternate layouts).

See attached schematic.

lma_schem3_A.pdf

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HELLO !

for a boy who say "I do not have time to develop alternate layouts"

I just reply : "Thank's very much Mr RC-CAM ! it's too much!!!"

I buy components today and i think i must do a pcb.

When it's finished and tested, i will post the picture layout and photo !

I promise ! :rolleyes:

Davidl

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Hello !

I would like to understand.

When the MAX8211 is inactive (U OK) the outpout of max8211 (pin 4) is high (5V) or the outpout N Channel is Blocked ?

The pic12C508 work good ?

The condenser C2 is present to do delay ?

The GND is connected to the potentiometer R5, is it not a mistake ?

If you have some time, thank's to explain me...

Davidl

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When the MAX8211 is inactive (U OK) the outpout of max8211 (pin 4) is high (5V) or the outpout N Channel is Blocked ?

The output is open (clamp off) when the voltage is OK. The R/C Signal is unaffected during this time. Upon low voltage, the output goes low and clamps the R/C signal to ground. This emulates a missing R/C signal.

The pic12C508 work good ?
Sorry, but I do not know what you mean.
The condenser C2 is present to do delay ?
It is a filter for ripple suppression on the monitored input.
The GND is connected to the potentiometer R5, is it not a mistake ?

It is not a mistake. The pot is used as a traditional attenuator.

Note: Before I published this for you I built the circuit. It works fine on the bench. I have not validated it using the actual operating conditions of various model airplanes. If you run into any unwanted behavoir then you will need to alter the circuit to suit your needs. All the details of the MAX8211 IC are in its data sheet.

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