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This mod will make your Omnitech GPS unit power on whenever external power is connected to it. It is intended for those that would like their units to turn on when they turn on their car. After performing this mod, connecting external power will cause the following to happen depending on the state of the unit:
1. Completely powered off. -> It will begin boot up process.
2. In standby mode. -> The screen will flash once and come out of standby.
3. The unit is turned on and running a program -> The screen will flash once but remain on.
Disconnecting the power will have no effect on the unit. An unintended side effect of this mod is that the power button becomes disabled when external power is connected. The hard reboot button is not effected. When the external power is not connected, it behaves as if the mod is not there (the power button works).
Although this may look like an easy mod, you can easily ruin your unit. You need to have some soldering experience and be comfortable with electronics.
What you will need:
2 x 680 Ohm resistors
1 x 51 Ohm resistor
2 x 1000 uF capacitors*1
2 x 220 uF capacitor*2
1 x 4.5 V mini relay
1 x 5V relay*3
thin gauge wire
soldering equipment
*1. Not exactly the same capacitors I used. Mine came from here. The one in the link above is slightly longer. But shipping will kill you if you order from both sites and Jameco doesn't have the correct relays (coil resistance is very important).
*2. I used a single 475uF capacitor that I had laying around, but the substitution above should work.
*3. The relay I used came from this assortment, but there is no guarantee that you will get the exact same one. The important characteristics of the relay are: 5V, ~307 Ohm coil resistance, non latching. The mini relay has a coil resistance of 167.5 Ohms (measured) and is non latching as well.
1. Completely powered off. -> It will begin boot up process.
2. In standby mode. -> The screen will flash once and come out of standby.
3. The unit is turned on and running a program -> The screen will flash once but remain on.
Disconnecting the power will have no effect on the unit. An unintended side effect of this mod is that the power button becomes disabled when external power is connected. The hard reboot button is not effected. When the external power is not connected, it behaves as if the mod is not there (the power button works).
Although this may look like an easy mod, you can easily ruin your unit. You need to have some soldering experience and be comfortable with electronics.
What you will need:
2 x 680 Ohm resistors
1 x 51 Ohm resistor
2 x 1000 uF capacitors*1
2 x 220 uF capacitor*2
1 x 4.5 V mini relay
1 x 5V relay*3
thin gauge wire
soldering equipment
*1. Not exactly the same capacitors I used. Mine came from here. The one in the link above is slightly longer. But shipping will kill you if you order from both sites and Jameco doesn't have the correct relays (coil resistance is very important).
*2. I used a single 475uF capacitor that I had laying around, but the substitution above should work.
*3. The relay I used came from this assortment, but there is no guarantee that you will get the exact same one. The important characteristics of the relay are: 5V, ~307 Ohm coil resistance, non latching. The mini relay has a coil resistance of 167.5 Ohms (measured) and is non latching as well.
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Signing UpStep 1Dismantle and Conquer!
1. Remove the 4 Philips screws on the back cover.
2. Lift off the the back over, and disconnect the battery and speakers from the main board.
3. If you have added a microphone (previous instructable), you will need to de-solder the wires and tuck them out of the way.
4. Disconnect the GPS antenna by pealing up the copper sticker over the connector and gently popping the connector off.
5. Remove the two screws at the bottom corners of the main board.
6. Slide the main board down unit the clips at the very top no longer hold it down.
7. You can now swing the main board up. Be careful to not lose the power button as it will now be removable.
8. You have done all of this to access the leads to the power switch. It is a momentary switch. Solder on two wires to the leads of the power switch and run the wires to the other side of the main board. You can verify that you have done this correctly by briefly connecting the power to the unit and crossing those wires for a few seconds. The unit should power on. Now turn it off! We have work to do!
9. Place the main board back exactly as you found it. Connect the GPS antenna. You can solder the microphone back on as well.
10. Leave the two wires hanging there for now.
2. Lift off the the back over, and disconnect the battery and speakers from the main board.
3. If you have added a microphone (previous instructable), you will need to de-solder the wires and tuck them out of the way.
4. Disconnect the GPS antenna by pealing up the copper sticker over the connector and gently popping the connector off.
5. Remove the two screws at the bottom corners of the main board.
6. Slide the main board down unit the clips at the very top no longer hold it down.
7. You can now swing the main board up. Be careful to not lose the power button as it will now be removable.
8. You have done all of this to access the leads to the power switch. It is a momentary switch. Solder on two wires to the leads of the power switch and run the wires to the other side of the main board. You can verify that you have done this correctly by briefly connecting the power to the unit and crossing those wires for a few seconds. The unit should power on. Now turn it off! We have work to do!
9. Place the main board back exactly as you found it. Connect the GPS antenna. You can solder the microphone back on as well.
10. Leave the two wires hanging there for now.
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