Lost Model Alarm

13 February 2004

This project documents how to build and construct your own Lost Model Alarm (LMA) using a Microchip 12F675 PIC and a small number of standard components.

Important Note

This information is provided on a 'as-is' basis. Model aircraft are not toys. Construction, and use, of this device is at the users own risk.

Most simple PIC programmers do not verify that the device has been programmed correctly by using high and low supply voltages to the PIC. This type of programmer is not normally considered a production environment programmer and there is a risk that the PIC has not been correctly programmed even when the software says it has been.

Background

There are a number of commercially available LMAs and also a number of other projects for DIY LMAs.

The various commercial units, and DIY designs, offer a wide range of features and facilities. The features considered desirable differ widely from unit to unit. This design provides a number of features that I considered useful.

This project grew out of the desire to add a basic LMA to the Brushed Motor ESC project, to investigate LMAs this project was created as a separate standalone project.

In its simplest form this LMA operates without any signal from the receiver, the LMA will give a short beep at powerup and then the LMA will sound its alarm sequence after a fixed period from power on or if the battery voltage is too low. The alarm consists of a number of beeps that sound once every 30 seconds.

The more sophisticated versions of this LMA monitor one of the receiver channels and will sound the alarm on loss of signal. In addition the LMA can be configured to sound the alarm under explicit control from the transmitter.

A further facility of this LMA is the ability to count receiver glitches and to report on the number of glitches recorded.

In short, this LMA offers a range of facilities that the user can configure when constructing the LMA. The LMA can also be used for other tasks such as a low throttle glow plug driver.

What this LMA offers

This LMA design offers the following features, all features are configurable when the LMA chip is programmed:

Time based LMA activation, the LMA can be configured to turn the alarm on after between 1 and 255 minutes after power is applied.
Activation of the alarm after loss of received servo pulses.
Activation of the alarm when the received servo pulse is less than, or greater than, a specific value. The activation point is configured in the LMA at any time.
Monitoring of receiver glitches, these are servo pulses that are outside tolerances or too far apart.
Monitoring of battery voltage with a special alert sequence for the low battery condition.
The ability to drive a variety of output devices including: either AC piezo transducers, DC buzzers, LEDs or other devices. The LMA has two output pins which can either be configured to drive a single 50mA load, or two loads up to 25mA each. Note: that the LMAC configuration has only one 25mA output signal.
Configurable alarm sound, duration, silent period etc.

In most cases these options are separately configurable in the LMA and will operate together. For example it is possible to construct an LMA with Time Based Activate only, or Time Based Activation and Glitch Monitoring only, or any combination of the options mentioned above.

Time based activation

In its simplest mode of operation the LMA just waits for a period of time to expire and then turns on the alarm. Once the alarm is turned on due to the expiry of the time it will stay on until the battery is flat.

Activation on Loss of Servo Pulses

By monitoring a receiver channel the LMA can detect loss of valid signals. A valid signal is considered to be any received servo pulse in the range of 0.768ms to 2.559ms that occurs at least once every 25ms.

If valid pulses stop for a period exceeding 100mS the LMA alarm will activate. The alarm will be canceled if 10 valid receiver pulses in a row are detected.

Activation under command

The LMA can be configured to monitor a receiver channel and to activate the alarm if the servo position on the channel is above, or below, a particular setting. In order to activate the alarm the servo must be in the position for at least 250ms.

This facility is useful for users with a spare channel, or a channel that is not normally set beyond a particular point. The purpose is that when a model is lost, but still probably within range, the LMA can be triggered without either waiting for the time based activation or loss of signal activation. This stops servos etc. from flapping around when there is no receiver signal and possibly damaging the aircraft more, or using valuable battery power.

The command activation point may be either preset in the software or configured into the LMA during operation and is easy to alter at any time.

Glitch counter

The glitch counter system permits the LMA to monitor a receiver channel and count the number of glitches, any received servo pulse outside the range of 0.768ms to 2.559ms, or servo pulses more than 25ms apart.

The LMA can be commanded to 'beep out' the count of glitches using a small switch or jumper pins on the LMA.

Battery Voltage Monitor

The battery voltage monitor enables the LMA to monitor the supply voltage to the LMA. If the supply voltage drops below a voltage that is set during construction the LMA will commence sounding a special low voltage alarm sequence.

The LMA will exit the low voltage alarm sequence when the voltage is restored to a level above the detection point.

Output Devices

The LMA can control a variety of output devices, including directly driving AC Piezo transducers. The AC transducers offer the lowest cost alarm and have acceptable volume levels. (It is also possible to use two transducers to get increased volume levels.) The AC Piezo transducers have a specific resonant frequency and you must configure the LMA software with the resonant frequency of your transducer. To control AC transducers the LMA output signals are driven in a square wave and the appropriate frequency.

Alternatively the LMA can control DC buzzers, or Piezo units with inbuilt drivers, or may other devices. In this case the LMA output signals are driven to +volts when the alarm is to sound.

The LMA has two output signals that are each capable or sourcing 25mA. These outputs can be used independently to drive two output devices less than 25mA each, for example a buzzer and a LED, or joined together to drive a single device requiring up to 50mA.

Configurable

The LMA has many configurable parameters in the source code that users can adjust to get their desired mode of operation.

Software Development Environment

This software was developed with the MPLAB IDE from MicroChip. To build this LMA it is very likely that you will need to use this software to produce the .HEX file for programming your LMA. There are too many different configuration parameters to publish on the Internet all the possible LMA .HEX files.

After you have installed the MPLAB IDE proceed as follows:

Create a directory somewhere on your Windows system. the MPLAB IDE does not like path names that are too long (greater than 30 characters or so) - so stick to a simple short name. For example: C:\PIC\LMA
Copy the lma.asm file from the links below into your directory.
Start the MPLAB IDE.
Select Project->Project Wizard.
Click Next.
Select 'PIC12F675' as the device, click 'Next'.
Select 'Microchip MPASM Toolsuite' as the Active Toolsuite, click 'Next'.
Enter a name for your project and then use the 'Browse' facility to set the Project Directory to the directory you created at the first step, click 'Next'.
Add the lma.asm file that you copied into the project directory to the project by double clicking the file name in the left hand pane, the file will appear in the right hand pane. Do NOT check the box next to the file. Click 'Next'.
Click 'Finish'.
The workspace will open and you will see a project window that shows one Source File.
You should now be able to assemble the PIC code by pressing F10 - this will produce a file called 'lma.hex'.
To alter the parameters double click on 'lma.asm' in the project window and the assembler source will now appear in a new window, make the changes you require in this window.
After you have made you changes press F10 to assemble the code.

The MPLAB IDE has full support for simulation that permits you to fully check the operation of the LMA. However, the use of these facilities is beyond the scope of this document. Users who just want to build a 'custom' version by modifying standard parameters of the LMA should have no problem using the IDE to assemble and test their code.

The software options

The following step-by-step procedure will permit you to configure the LMA software for your application. There are 4 basic configuration values that need to be set, these values are at the top of the LMA source file and will look something like this in the standard file:
  POWERUPBEEP	equ	1	; 0 or 1
  LMARUNTIME	equ	0	; time in minutes that the LMA should turn on
  LMAONLOS	equ	1	; turn on LMA on loss of receiver signal
  LMAONCMD	equ	1	; 0,1 or turn on at < usec
  GLITCH_COUNT	equ	1	; 0 or 1
  LMAFREQUENCY	equ	4500	; 1 or frequency in Hz
  
This procedure will permit you to determine the value to assign to each parameter, you then use the MPLABS IDE to alter the source code and then press F10 to build the LMA.HEX file for programming the 12F675.

Determine if you have an AC siren, or a DC buzzer. The retailer should know which is which, I would suggest an AC piezo as the lowest cost and simplest to use. If you have an AC siren go to step 3.
You have a DC buzzer, set LMAFREQUENCY to 1. Go to step 4.
You have an AC siren, you need to know the resonant frequency in Hz. (If you have the frequency in kHz, for example 4.2kHz, then multiply the number by 1000 and you have Hz). Set LMAFREQUENCY to the frequency in Hz.
Determine if you want the LMA to turn on at nominated time after power up. If you do go to step 6.
You do not want the LMA to turn on at a nominated time, set LMARUNTIME to 0. Go to step 7.
You want the LMA to turn on after a specific time. You need to determine the time in minutes and it must be between 1 and 255. Set LMARUNTIME to the time in minutes.
Determine if you require the glitch monitor facility. If you want this facility go to step 9.
You do not require the glitch monitor facility so set GLITCH_COUNT to 0. Go to step 10.
You require the glitch monitor facility so set GLITCH_COUNT to 1.
Determine if you want the LMA to monitor the receiver pulses and activate the alarm on loss of signal. If you want this facility go to step 12.
You do not require the alarm to activate on LOS, set LMAONLOS to 0. Go to step 13.
You do require the LMA alarm to activate on LOS, set LMAONLOS to 1.
Do you require the LMA to activate on command? If you do not then set LMAONCMD to 0. Otherwise set LMAONCMD to 1 if you want configurable command point. For a fixed command on point when the receiver pulse is on at < X.YYYmsec set LMAONCMD to -XYYY, to command on at > X.YYYmsec set LMAONCMD to XYYY.
Determine if you want the LMA to produce a very short beep when powered on to indicate that it is functioning. If you want the this facility go to step 16.
You do not require the power up beep, set POWERUPBEEP to 0. Go to step 17.
You do require the power up beep, set POWERUPBEEP to 1.
Determine if you require low voltage detection in the LMA, if you do goto step 19.
You do not require low voltage detection, set LOWVOLTS to 0. Go to step 20.
You require the low voltage detection facility. Set LOWVOLTS to the desired low voltage indication point in mV. For example, 4.2V would be 4200. In addition you need to know the reference voltage you are using. If you construct the LMA as shown in the diagrams the reference voltage will be 3.3V (or 3300mV) and you do not need to alter the software configuration. If you have a different reference voltage you should set LOWVOLTSREF to the reference voltage in mV.
Software configuration is now complete.

Circuits

There are two possible basic circuits that will apply to your LMA. The simplest one is when there is no receiver channel to monitor (LMAA), the more complex (LMAB) is when there is a receiver channel to monitor. It does not matter if you use the more complex LMAB circuit with an LMA that only requires LMAA.

There are also a number of possible alarm device connections and these are shown on a separate diagram. You will need to select from the possible alarm device configurations that suit your requirements.

You can determine the circuit that your LMA requires by loading the LMA.HEX file into your PIC programmer and looking at the text display of the PIC contents you will see the file name, version number, and circuit type displayed in the text area.

Where is everything?

The files available for download are:

File Name Description

lma.asm Ver 1.2: PIC 12F675 Assembler Source

lmaa.gif Rev B: Circuit diagram for basic LMA - LMAA

lmab.gif Rev B: Circuit diagram for complex LMA - LMAB

lmac.gif Rev A: Circuit diagram for complex LMA - LMAC

lmaalrm.gif Rev B: Circuit diagram showing various LMA alarm options

File Name	Description
lma.asm	Ver 1.2: PIC 12F675 Assembler Source
lmaa.gif	Rev B: Circuit diagram for basic LMA - LMAA
lmab.gif	Rev B: Circuit diagram for complex LMA - LMAB
lmac.gif	Rev A: Circuit diagram for complex LMA - LMAC
lmaalrm.gif	Rev B: Circuit diagram showing various LMA alarm options

How to build one

So after all that you would like to try constructing one of these, what do you do?

Because of the large number of options possible for the LMA this section is a guide only. The pictures shown in this section are for the construction of an LMAB design with a single AC piezo siren using the soldered leg construction system.

This LMA when fully assembled weighs 10gms (+/- 2gms).

Step Description

1
Purchase your components.

I would suggest a machined pin 8-pin socket to hold the PIC. These sockets last longer and also have more robust legs for this construction technique.

The servo cable can be purchased with only one connector and bare wires on the other end. Alternatively, you may want to consider purchasing a 300mm servo extension lead and cutting it in the middle you can then join the wires together and form an extension cable with the LMA in the middle, or constructed as a Y-cable with the LMA at one end.
You also need to select a piezo, buzzer or LED for the alarm output. If using an AC piezo transducer you can build a louder unit by using two transducers, one on each output.

2
If you are constructing the LMAB circuit you will need either a small push button switch, or a 2 pin header. This switch is required for programming the LMA command point, and also for obtaining the glitch count. A 2 pin header block is quite suitable, you can use a normal PC jumper to close the contacts during command programming, and to obtain the glitch count just short the pins together with a coin or something. If you prefer a small switch is also a possibility.

This example uses a 2 pin header block. These are normally sold in longer strips and you just break off two pins.

3
Decide if you need a small piece of veroboard to assemble your LMA on. In many situations you may just be able to assemble the components together just by soldering to the legs of the 8-pin socket. This is particularly suitable of the entire LMA and piezo is going to be glued together and then covered with a piece of heat-shrink tubing.

Alternatively for a more complex LMA with multiple output devices you may want to use a small piece of veroboard to hold the components. This technique is more suited when you want to construct an LMA that will be permanently installed and you don't need to cover the LMA - just build it into the plane.

This example uses the soldered leg construction technique.

4 Take the 8-pin socket and solder the fixed wires between pin 3 and 5. Note that the socket has a notch to indicate which end of the socket is pin 1 and 8.

5 Then attach the two capacitors C1 and C2 across pins 1 and 8 of the socket. Check the polarity of C2 carefully to ensure that the +ve goes to pin 1 of the socket.

6 Tin the end of the servo lead, or leads if you are making a Y-cable at the same time, that serves as the power and servo signal input to the LMA. If you are constructing the LMAA circuit you should cut off the servo signal and insulate it with a small piece of heat shrink tubing. For the LMAB circuit attach R2 to the servo signal and cover with heat shrink tubing.

7 Now attach the servo cable to the power supply pins and also R2 to the servo input signal (pin 6) if you are constructing LMAB. Take care to connect the power to the 8-pin socket the correct way round. The positive volts must go to pin 1.

8 If you are constructing LMAB you now need to connect the switch and its associated resistor to the PIC. Do this in such a way that the switch, or header pins, are going to be accessible once construction is complete.
This is best done soldering R1 between pins 1 and 4, and then the switch, or header pins, between pins 4 and 8. You may need to use a short length of insulated wire to help join these components up.

9 Connect the buzzer, siren or LEDs that you are going to use with the LMA. Again if you are installing a high intensity LED ensure that it is oriented so the lens will be visible once construction is complete.

10 Now is the time to test your LMA and ensure correct operation of the LMA. See below for the test procedure.

11 If you are going to join the piezo and LMA into a single unit use a small amount of hot glue, RTV silicon, or similar product to attach the 8-pin socket to the back of the Piezo. Note: ensure that the piezo's vent hole is on the outside and also that the IC socket is mounted so that the chip can be changed.

12 You can now shrink a piece of heat shrink onto the LMA. After shrinking the tube cut the tubing away to expose the piezo vent hole - otherwise you won't get much sound.

13 Follow the user instructions below.

Step		Description
1		Purchase your components. I would suggest a machined pin 8-pin socket to hold the PIC. These sockets last longer and also have more robust legs for this construction technique. The servo cable can be purchased with only one connector and bare wires on the other end. Alternatively, you may want to consider purchasing a 300mm servo extension lead and cutting it in the middle you can then join the wires together and form an extension cable with the LMA in the middle, or constructed as a Y-cable with the LMA at one end. You also need to select a piezo, buzzer or LED for the alarm output. If using an AC piezo transducer you can build a louder unit by using two transducers, one on each output.
2		If you are constructing the LMAB circuit you will need either a small push button switch, or a 2 pin header. This switch is required for programming the LMA command point, and also for obtaining the glitch count. A 2 pin header block is quite suitable, you can use a normal PC jumper to close the contacts during command programming, and to obtain the glitch count just short the pins together with a coin or something. If you prefer a small switch is also a possibility. This example uses a 2 pin header block. These are normally sold in longer strips and you just break off two pins.
3		Decide if you need a small piece of veroboard to assemble your LMA on. In many situations you may just be able to assemble the components together just by soldering to the legs of the 8-pin socket. This is particularly suitable of the entire LMA and piezo is going to be glued together and then covered with a piece of heat-shrink tubing. Alternatively for a more complex LMA with multiple output devices you may want to use a small piece of veroboard to hold the components. This technique is more suited when you want to construct an LMA that will be permanently installed and you don't need to cover the LMA - just build it into the plane. This example uses the soldered leg construction technique.
4		Take the 8-pin socket and solder the fixed wires between pin 3 and 5. Note that the socket has a notch to indicate which end of the socket is pin 1 and 8.
5		Then attach the two capacitors C1 and C2 across pins 1 and 8 of the socket. Check the polarity of C2 carefully to ensure that the +ve goes to pin 1 of the socket.
6		Tin the end of the servo lead, or leads if you are making a Y-cable at the same time, that serves as the power and servo signal input to the LMA. If you are constructing the LMAA circuit you should cut off the servo signal and insulate it with a small piece of heat shrink tubing. For the LMAB circuit attach R2 to the servo signal and cover with heat shrink tubing.
7		Now attach the servo cable to the power supply pins and also R2 to the servo input signal (pin 6) if you are constructing LMAB. Take care to connect the power to the 8-pin socket the correct way round. The positive volts must go to pin 1.
8		If you are constructing LMAB you now need to connect the switch and its associated resistor to the PIC. Do this in such a way that the switch, or header pins, are going to be accessible once construction is complete. This is best done soldering R1 between pins 1 and 4, and then the switch, or header pins, between pins 4 and 8. You may need to use a short length of insulated wire to help join these components up.
9		Connect the buzzer, siren or LEDs that you are going to use with the LMA. Again if you are installing a high intensity LED ensure that it is oriented so the lens will be visible once construction is complete.
10		Now is the time to test your LMA and ensure correct operation of the LMA. See below for the test procedure.
11		If you are going to join the piezo and LMA into a single unit use a small amount of hot glue, RTV silicon, or similar product to attach the 8-pin socket to the back of the Piezo. Note: ensure that the piezo's vent hole is on the outside and also that the IC socket is mounted so that the chip can be changed.
12		You can now shrink a piece of heat shrink onto the LMA. After shrinking the tube cut the tubing away to expose the piezo vent hole - otherwise you won't get much sound.
13		Follow the user instructions below.

Test Procedure - LMAA circuit

Note: during testing the alarm may sound and could be very loud. You may want to muffle the siren or buzzer while working on the unit to reduce the volume.

TIP: If you want to reduce the noise of the piezo or buzzer when testing, just put a piece of thick tape over the orifice - this cuts the noise way down and saves your ears.

Ensure that there is no PIC installed in the IC socket.
Plug the servo cable into a receiver channel and connect the receiver to a battery pack.
With a multi-meter check the voltage between pins 1 and 8 - pin 1 should be 4.8V (5V if you are using a BEC).
If you have configured the LMA for low voltage detection check the voltage between pin 6 (T1) and pin 8. Pin 6 should show 3.3V, if it does not then check the wiring and also the polarity of D1.
Remove the battery pack.
Check the software options using the information in the section above. Generate the LMA.HEX file.
Load the LMA.HEX file into your programming software and check the text display of the PIC contents to ensure that it specifies the circuit type you expect.
Program a PIC with this code.
Insert the programmed PIC into the socket.
If you are constructing an LMAA circuit your LMA will only activate based on run time. Apply battery power to the receiver. There should be no alarm active at this point. Check the voltage between the alarm driver pins and ground - there should be 0 volts.
Now you need to wait for the number of minutes that you configured into the LMA. After this time the alarm should start sounding. If the alarm does not sound check the voltage between ground and the alarm driver pins. When the alarm is active you should measure either a DC or AC voltage of 4.8V on the alarm driver pins.
To check the low voltage detection you can connect the LMA to a known low voltage battery pack. Alternativly you can use a 3.6V supply such as a 3 cell pack. The low voltage alarm should sound.
The test is complete.

Test Procedure - LMAB & LMAC circuit

Note: during testing the alarm may sound and could be very loud. You may want to muffle the siren or buzzer while working on the unit to reduce the volume.

TIP: If you want to reduce the noise of the piezo or buzzer when testing, just put a piece of thick tape over the orifice - this cuts the noise way down and saves your ears.

Ensure that there is no PIC installed in the IC socket.
Plug the servo cable into a receiver channel and connect the receiver to a battery pack.
With a multi-meter check the voltage between pins 1 and 8 - pin 1 should be 4.8V (5V if you are using a BEC).
With a multi-meter check the voltage on pin 4 of the socket. This should be 4.8V when the switch is not pressed and 0V when the switch is pressed. If this is not correct check your wiring.
If you have constructed the LMAC curcuit for low voltage detection check the voltage between pin 7 (T4) and pin 8. Pin 7 should show 3.3V, if it does not then check the wiring and also the polarity of D1.
Remove the battery pack.
Check the software options using the information in the section above. Generate the LMA.HEX file.
Load the LMA.HEX file into your programming software and check the text display of the PIC contents to ensure that it specifies the circuit type you expect.
Program a PIC with this code.
Insert the programmed PIC into the socket.
Turn on your transmitter. If you have configured activation under command you should set your transmitter to a setting that indicates you do not want the alarm on.
Apply the battery power.
If you have not configured the LMA for programmable activation point you should skip to step 23.
If you have configured the LMA for a programmable activation point the beeper should start sounding the 'not programmed' code of one short followed by one long beep that is repeated forever. If this does not occur you should check the alarm driver connections.
Remove the battery power.
Hold down the switch, or place the jumper on, and reapply power.
The LMA should produce one short beep to indicate that programming mode has been entered.
Move the transmitter control to the extreme position that should cause the LMA to activate.
Release the switch, or remove the jumper.
The LMA will produce one short beep, followed a short time later by two short beeps that indicate the position has been read. If the LMA produces the 'not programmed' code (one short followed by one long beep) then you have a problem in the receiver pulse wiring (or the transmitted is turned off).
Move the transmitter control away from the activation position to the normal limit position (where you do not want the LMA activated). The LMA turn on point will be set midway between this position and the previous position.
Press and release the switch, or connect and remove the jumper. The LMA will produce the 'programming complete' code.
When you do not have a programmable activation point, or have just completed programming mode, the LMA should be silent. If you hear the LMA alarm (a series of rapid beeps every 30 seconds) you have a problem with the receiver pulse wiring (or your transmitter is turned off).
If the LMA is configured for activation by command move the transmitter control to that position - the LMA alarm sequence should comments. Move the transmitter control to the normal position and the alarm should stop.
If the LMA is configured for activation on loss of servo pulse turn the transmitter off - the LMA alarm sequence should commence. Turn the transmitter back on and the alarm should stop.
If you have the glitch counter configured into the LMA try pressing and releasing the button, or temporarily shorting the jumper pins. The LMA should indicate the number of glitches so far by sounding the beeper to indicate a number between 0 and 99.
To check the low voltage detection for LMAC you can connect the LMA to a known low voltage battery pack. Alternativly you can use a 3.6V supply such as a 3 cell pack. The low voltage alarm should sound.
Your LMA should now be fully functional. Testing is complete.

User Instructions

Programming the activation point

Remove power from the LMA.
Turn on the transmitter.
Hold down the switch, or place the jumper on, and reapply power.
The LMA should produce one short beep to indicate that programming mode has been entered.
Move the transmitter control to the extreme position that should cause the LMA to activate.
Release the switch, or remove the jumper.
The LMA will produce one short beep, followed a short time later by two short beeps that indicate the position has been read. If the LMA produces the 'not programmed' code (one short followed by one long beep) this indicates that a stable received pulse was not available - either the transmitter is turned off or there is no receiver pulse for some other reason.
Move the transmitter control away from the activation position to the normal limit position (where you do not want the LMA activated). The LMA turn on point will be set midway between this position and the previous position.
Press and release the switch, or connect and remove the jumper. The LMA will produce the 'programming complete' code.

Obtaining the glitch count

Press the button, or short the header with a coin.
The LMA will beep the number of glitches it has registered.

If there have been no glitches a single long beep will sound.
If there have been more than 99 glitches two long beeps will sound.
For between 1 and 9 glitches than number of short beeps will sound. For example, 4 glitches will sound four short beeps.
For between 10 and 99 glitches the LMA will beep out the tens and then the units with a pause between them. A unit of zero is indicated by a long beep. For example, 13 glitches would be 1 short beep, a pause, and then 3 short beeps.

LMA codes

Sound	Meaning
1 very short beep	LMA Startup Sequence Indicates that the LMA is operating. This code should occur immediately after power up, or when programming is complete.
2 very short beeps once every 30 seconds	LMA Alarm Sequence The LMA alarm condition is active.
1 very short beep once every 5 seconds	Low Battery Sequence The LMA has detected a low battery condition.
Short beep, long beep repeated	Not Programmed The LMA is configured for programmable activation point and this point has not yet been configured. Power the LMA off and follow the instructions for programming the activation point.
Long beep repeated	Programming Failure The LMA is in programming mode however programming cannot be completed. Power the LMA off, check that the transmitter is turned on and attempt the programming again. There is a possiblility that this will occur if the programmable storage in the PIC is faulty, however, normally it indicates that the receiver servo pulses are not present.
Single short beep	Entering programming mode The switch was pressed at power up and the LMA has entered progamming mode. Various sequences of short beeps will guide you through programming mode.
Three short beeps	Exit programming mode The LMA has completed programming and is enntering normal operating mode.
Other Sequence	Glitch monitor output The glitch monitor indicates the number of received glitches

Frequently asked questions

Q: I want to control the LMA using the gear switch how do I configure this?

A: Set the gear switch to the position that you want the LMA activated in. Hold down the switch and apply power. When you hear the single beep release the switch. When you hear the the two short beeps move the gear switch to the normal position and then press and release the button. The LMA will sound the programming complete code. The LMA will now activate when the gear switch is moved to the activation position.
Q: How do I get a louder sound?

A: You can increase the volume in a number of ways:

Use two piezo transducers, one on each output.
You can use a different buzzer or siren with a higher output. Just remember that the PIC can only drive 25mA per output pin. A higher current that this would require a transistor or FET buffer.
You can power the buzzer from a separate battery using a transistor or FET buffer.
You may be able to modify a 'personal alarm' keyring or similar device to be controlled by the LMA.
Various of these options are shown on the circuit diagrams.
Q: Can I use this LMA for anything else?

A: Yes, the LMA can be used as a switch for various purposes. It is really only a programmable switch with a number of configurable parameters.
For example, to use the LMA PIC as a glow switch that turns the glow plug on at low throttle proceed as follows: set LMARUNTIME to 0, LMAONLOS to 0, LMAONCMD to 1, LMAFREQUENCY to 1 and GLITCH_COUNT to 0. Build the LMAB circuit with a LED on one output pin, and a FET or transistor driver controlling the glow power supply on the other alarm output.
To set the turn on point proceed as follows: set the transmitter throttle to the point that turn on is required, hold down the LMA switch, power the LMA and receiver on, wait for programming mode to commence as indicated by the LED, release the switch, wait for the continue code to be indicated on the LED, move the throttle one click higher (where the glow pulg should not be driven), press and release the switch, programming will now complete.
The glow drive is indicated on the LED for diagnostic purposes. The glow drive will be turned on whenever the throttle is below the throttle position set during configuration.