MIC-LITE.TXT The NEW Smaller-Cheaper Mic-Lite Copyright 1999 =========================================================================== Document version: 8.4.1 Document dated: 12 May 99 Author(s): Bob Bruninga, WB4APR MIC-LITE.TXT The MIC-LITE is just the ubiquitous MIM module configured as a more compact APRS Mic-Encoder for half the price. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ See also MIM.TXT For details about the MIM module TELEMTRY.TXT Details the telemetry aspects MIC-E.TXT The original Mic-E documentation The Mic-Lite is the ultimate APRS Mic-Encoder for maximum flexibility and versatilty. It can be plugged into any radio in place of the microphone and gives you instant APRS position, telemetry and message reporting on any Radio. It is assembled from the MIM Module and a few off- the shelf Radio Shack components. This Mic-Lite design solves many of the complications of the original APRS Mic-E for lightweight and portable applications. It solves the plethoria-of-mic-connectors problem by including an electret Microphone element and its own PTT within the Mic-Lite enclosure. Further it solves ground loop and power supply problems by operating from its own internal battery. Finally it solves the interface problem of combined PTT/Mic-Audio as used on most HT's. For most ICOM, Alinco, Yeasu and other HT's, only a single sub-mini phone plug is required. Kenwoods require two plugs and an external earphone. Since the Mic-Lite is completely self-contained and runs on its own internal battery or Mic power, its best application is for special events where rapid configuration and portability are important. The internal 9v battery should last about 60 hours or over a month of typical commuting. The battery voltage is included in the telemetry packets so predicting battery replacement is easy to do. For mobile rigs, microphone power can be used instead of the internal battery. ASSEMBLY: The Mic-Lite is a good evening construction project. Purchase the wired-and-tested MIM as indicated below, and then visit your local Radio Shack to pick up the remaining components for under $10 (you will pay slightly more since many components are packed 2 or more per package). The MIM module uses the same chip and firmware used in the TAPR Mic-E, and can be configured at any time in either the MIM or Mic-E mode. Since the bulk of the TAPR Mic-E is due to the front panel controls, Mic connectors and room for an internal GPS, this file shows how to use the basic MIM to make a much smaller and cheaper one called Mic-Lite(tm) MIC-LITE: The full size TAPR Mic-E has two 16 position thumb wheel switches and a PERIOD pot to give the operator full control over Mic-E operations. For the Mic-Lite, most of these can be wired to small dip switches, replaced with single toggles or just jumpered to defaults with no switches. With no switches it can even be integrated inside the radio! Many routine applications of the Mic-E concept can be set to a default condition and front panel controls are unnecessary. Here is a table showing various levels of control. Front Panel PATH Switch MSG Switch RATE AUTO -------------- ----------- ----------- -------- ----- Thumbwheels 16 paths 7 msgs Pot 1-16 On/Off 10 pos Dip Sw 16 paths 7 msgs Hi/Low On/Off Four switches 2 paths two msgs Hi/low On/Off Three switches 2 paths One msg Hi/low ON/OFF Two switches one path one msg Hi/Low ON/off One switch one path one msg Hi/Low ON or OFF No switches one path one msg HI or LOW ON or OFF I consider the Hi/Low to be the most important since it not only allows switching between "driving" and "parked", but also it triggers a "report now" whenever it is toggled. The next most important in some applications is the AUTO switch, since it allows you to operate in Mic-E mode on a voice repeater, or go to auto mode on 144.39 as a stand- alone tracker. PACKAGING: There are five basic ways to package a Mic-Lite: * IN-RADIO: This is easiest installation, but requires internal radio work and adding an external GPS jack. It also lacks front panel control which may or not be good. * IN-MIC: This works well for mobile radios with room in their big Mic's when you can power the Mic-Lite from the mic power. You must add a GPS jack to the Mic enclosure and may want to add some buttons or switches. Wire the Hi/Low Period input to the UP button the Mic, and then any time you want to trigger a NOW packet, just press the UP (and then DN). The UP button still works as an UP button too! I got a MIM to fit in a very small Alinco TTONE mic! See also section on powering. * IN-LINE: This either requires mic-in and out jacks so you can insert the Mic-Lite between the Mic and the Radio, or attaching it in parallel at the Mic connector on a dangel. This makes it easy to place anywhere for button access. * NEW-MIC: This just adds an electret Mic and PTT to a small plastic case on which you can put any/all buttons you want. In effect, you are building your own Mic-E in your own Microphone case. Actually this is the most flexible option when included with a battery. * FOR-HT: This arrangement is any of the above options, but uses its own internal battery so that it is trivial to plug into ANY radio (HT) with out any concern over power. STAND-ALONE-MIC-E: This is the NEW-MIC and FOR-HT combination which I think is the most flexible. It builds the Mic-Lite into a small Mic enclosure with internal 9v battery so that it can plug into ANY radio or HT at the Mic Connector. The GPS then plugs into it. Here is the easy way to build this using the small plastic mini-box from Radio shack. Notice that it includes its own Electret Mic element to make it a completely self contained Mic-Encoder. Total parts cost at Radio Shack is $6.75 plus the MIM and Battery. *** PTT PTT SW RS# 275-1547 $0.75 +----------| |------------+ | OOOOO | | | | OOOOO +---+ | Electret Mic RS# 270-090C $2.00 | (mic) +--------------|| |+-----------+ || Proj Box RS# 270-1801 $2.00 || | ----- || || | | M | || || 9 Volt | | I | || || | | M | || Optional DIP switch to select message || BATTERY | | | || and/or PATH and/or RATE not shown || | | C | || || | | H | || || | | I | || || | | P | || ||-----------| ----- || Box is 3" by 2" by 1" | +--------------+| | +---+ | | || || | +----------| |------------+ -^- GPS Jack Phone Jack RS# 274-249 $1.00 Mic Plug to HT RS# 274-289 $1.00 HARDWARE CONFIGURATION: The MIM is simply connected between the Microphone and the radio. For Handi-Talkies with combined PTT such as ICOMS, Yeasu Alinco's and most FRS radios, simply use a 3k and 100k resistor to join these two to a sub-mini phone plug as shown below. +--+Electret Mic | |---------------------------------------------*--------> AUDIO/PTT | |--* | to RADIO +--+ | +------------------+ 100k | | d1 | TXA*----/\/\/---* PTT | *--|<------*D0 MIM PTT*----/\/\/---* Button | * | | 3.3k | | MODULE RXD*------------------* | | G G TXD*---------------*> | | +--*----------*----+ <* | | | ==== *-------------*----------*--------------------====--> GND GPS JACK GPS/SERIAL PORT CONNECTOR: Please consider using a 1/8th inch stereo mini jack for the GPS connector as shown. This is the same data connector used on the TAPR Mic-E, the PacComm Handi-Packet, and the Kenwood HT (though the Kenwood is a sub-mini 3/32, but the wiring is the same and only needs a RS adapter part # 274-397. TIP is DATA-OUT and RING is DATA-IN. Connect the GPS to DATA-IN. CIRCUIT DESCRIPTION: Diode d1 lets the MIM sense PTT while also providing isolation to prevent the MIC-E from grounding the PTT lead when the MIC-E is turned off. The 100k audio resistor isolates the MIM so it does not load down normal Mic audio, and the 3k combines the DC PTT signal onto the Mic lead. For Kenwoods or other radios with separate PTT lines, then the following circuit is needed on the PTT circuit. Here diode d2 lets either the PTT-IN or the MIM key the radio. The points P--P show where to add a PTT LED if desired. d2 PTT IN >--*----------------|<----------------*-------> PTT to RADIO | d1 +---------------+ | *----|<----*D0 MIM PTT*P------P +---------------+ PATH and MESSAGE SWITCHES: Not shown in the schematic above are any of the optional PATH, MESSAGE and PERIOD connections. If unconnected, then the bits are considered a logic "0". Bits D2 to D8 connect the PATH and MESSAGE switches and A3 is the PERIOD adjust pot as follows: D7 D6 D5 D4 D3 D2 D1 +5v +5v +5v HOLDOFF * * * * * * * * * * * | | | | | | | | | | | +----------+ +-------+ 10k | | | | | | | | | / 10k * AUTO | 7 | | 7 | *-->A0 | \ <----* A3 / sw | P A T H | | M S G | | | / * +----------+ +-------+ 2.4k | \ PERIOD | | | | | | POT | GND GND GND A1 GND GND Note that A1 must be jumpered to +5 to enable the currently used DIGI mode instead of SSID mode. For the Mic-Lite, needing only to switch between R,W,W and W,W,W, simply ground D4 and D5 and add a select switch to D6. D7 is unused until we begin using directional and SSID routing some time in the future. A0 is connected to a 10k/2.4k voltage divider so that telemetry includes the battery voltage. A3 sets the PERIOD and the HOLDOFF pin may be connected to an AUTO switch, or GROUNDED. MESSAGES: You can choose any number of switches and combination diodes to select any messages as follows: No switches Off duty GND D1 Enroute GND D2 In Service (Note AUTO PERIOD CIRCUIT BELOW) GND D1&D2 Returning GND D3 Committed GND D3&D1 Special GND D3&D2 PRIORITY GND D3&D2&D1 EMERGENCY! Trips alarms & centers all maps to unit PERIOD POT: You can use a PERIOD POT or a 10k Pullup resistor and switch to control the "period" on input A3. With the switch open the +5 pullup will result in 16 times the programmed period. Grounding A3 will result in a POSIT-NOW and the pre-programmed rate. Or just hook to an existing Mic UP/DN button to serve as a POSIT-NOW button. See the section below on Automatic PERIOD adjustment between IGNITION on and IGNITION off. PTT READY LED: You can add an LED to the PTT circuit to see when the Mic-E has a packet scheduled. You may want to talk a little longer and wait till a packet is ready before you release the PTT. To do this, add diode d3 to isolate the LED from the normal PTT circuit and connect at points "P" shown in the above PTT circuit. d3 P*---*--|<-----*P | *--|<---/\/\/----*5v LED 1k GPS ACTIVE LED: To see when the GPS has good RMC data, connect an LED to the TXD data line as follows: LED 2.2k TXD*---|<---/\/\/---*5v BATTERY VOLTAGE TELEMETRY: Connect analog input pin A0 to a 10k/2.4k voltage divider so that your telemetry will contain your battery voltage. This combo makes 9v approximately equal to a telemetry value of 90. Or use a 5k pot in place of the 2.4k to tweak it exactly. Thus you can see the voltage of your battery to the tenth of a volt. AUTOMATIC PERIOD ADJUSTMENT: Although the front panel PERIOD pot makes it easy to adjust your reporting rate, you can make it automatic between a short period when the engine is running and a long period when it is parked using the following circuit: EXISTING PERIOD POT 5v *---/\/\/\/\/-------------* GND | 10k *---/\/\/\/--*----> A3 RATE INPUT | *---/\/\/\---* Ignition 56k |/c R Switch <---/\/\/\----| |\e NPN *-----------------* GND NOTE 1: The 10k resistor in series with the existing PERIOD pot input is there so that the new automatic circuit can share the input as shown. NOTE 2: You can connect the collector to message bit D1 and this will change your message between OFF DUTY and IN SERVICE automatically! NOTE 3: Software program your Mic-E to a peak rate of 1 minute so the the 16:1 front panel PERIOD pot gives you a range of 1 to 16 minutes. The added transistor and new value R are switched in when the ignition switch is on. ALthough the front panel PERIOD pot can still override to any setting, set it normally to your desired max value, say 16. Now then you can choose R to give you: PANEL POT will set the maximum period when the ignition is off. R = 0 will always force the peak rate no matter where the pot is R = 2k will force at least a MAX/8 rate R = 4k will force at least a MAX/4 rate R = 10k will force at least a MAX/2 rate (These values are approximate, your milage will vary) POWERING THE MIC-E: Although the Mic-E can be powered by the Mic power in some cases, the problems with alternator whine, GPS and processor digital noise on the power bus can be a big problem when interfacing to the mic connector of a mobile radio. If the GPS is also on internal batteries, then Microphone power should work fine. But if the GPS is externally powered by the vehicle battery, then you will surely have ground loop problems unless you are careful about grounding. The safest option is to use a 9v battery. It should last a month at 2 hours a day. See Mic-E.txt for other options. To minimize GPS noise, you may want to insert additional resistance in the GPS data line. See if 100K will work? MICROPHONE-POWER: Note, in the simple circuit shown above, the electret mic element is also powered by the PTT voltage. If you build a Mic-Lite for any other microphone circuit, then you will need to provide a few volts of power for the mic element too. Add the two resistors and two caps in the circuit below to make sure the 8 volt microphone jack power (which is also powering the MIM) is clean enough for the mic: *-----/\/\/------*-----/\/\/-----*---> 8v | 3.3k | 3.3k | | === 1uF === 10 uF Electret Mic | (mic power) | | +--+ | GND GND | |-----------------*---------------------------*--------> Mic Audio | |--* | +--+ | d2 | *-------------------|<---------------------|----*---> PTT | +------------------+ 100k | | | d1 | TXA*----/\/\/---* | PTT | *--|<------*D0 MIM PTT*-----------------* Button | * | MicGND*---------------------> Mic GND | | | | | +V *---------------------> 8v | | MODULE RXD*-----------------* | | G G TXD*--------------*> | | +--*----------*----+ <* | | | ==== *-------------*----------*-------------------====---> CKT GND GPS JACK RECEIVER DETECTOR/AUTO MODE: If you want to operate in AUTO mode with carrier detect for collision avoidance (Not really needed for the Mic-Lite, since your EAR can tell you when to press PTT), add the following audio receive circuit to amplify the speaker audio high enough to trigger the hold off circuit. (This circuit has not been tested). Holdoff <----*----*-----* | | c\| Q2 NPN S1 * | |--------*-----||-------------< RCV AUDIO \ | e/| | .2 uf * === | - | | 5uF | ^ d4 GND >--------*----*-----*----------*--------------------> GROUND Q2, d4 and the two caps are an audio rectifier to drive the HOLDOFF input to the MIM when the radio is in use. This keeps the MIM from sending a packet. S1 is the AUTO switch. It can be used with or without this circuit. When it is shorted to ground, then this is the same as an "always busy" channel, so the Mic-Lite will never auto-initiate a packet. (It still will do the Mic-E function on release of PTT). de WB4APR, Bob