Ron Gasser is a colleague I’ve known for years. He and I regularly email back and forth regarding technology, cameras, lenses, Photoshop and other techniques. He’s a great photographer and he’s also intently interested in incorporating technology into his craft.
Recently, he sent me information on making your own GPS unit for a Nikon camera. It is a very cool application, but kind of technical. I asked him if I could post this DIY topic on the blog and he agreed. Here’s the post, directly from Ron. By the way, you can contact Ron Gasser here: [email protected]
The construction of this GPS unit is relatively simple but does require some skills with electronics and the use of a Dremel tool for the box construction. The user can test the various components before assemble but this is not necessary as the items are properly configured as they arrive from the suppliers. This idea is not the brain child of this author but the accumulation of knowledge from others and the internet. The basic concept was done by many others. You can reference this web site “http://www.stockholmviews.com/diyphotogear/nikon_mc-35.html” for some background.
The construction can take many forms. One can add a switch to the item to control the power to the GPS but this is likely not needed and provides further complication. This author did not include a power switch as the room in the box is very limited. Plus, the construction practice used allows the final box to be totally sealed from the elements. Should one wish to remove power from the GPS, it is very easy to just unplug the unit from the camera.
The GPS unit has a LED that provides status of the location fix. When the LED is off, the unit is not getting power. When the LED is steady, the unit is acquiring a fix. When the LED is blinking, the GPS unit has a fix. Again, providing a view port for this LED is trouble. It requires another hole in the box and reduces the protection from the elements. The status of the GPS is provided on the camera bodies by the GPS symbol. When the GPS symbol is blinking, it indicates the GPS unit is talking but does not have a fix. When the GPS symbol is steady, the camera is recording the GPS fix.
The actual GPS unit is water proof BUT the electronics of the MC-35 cable is NOT. If you seal the box with epoxy, you can make the final assemble near water proof.
There is no high voltage or risks for the assembler, BUT the author does not take responsibility for the proper construction, assembler personal safety, camera damage or other difficulties one might experience. You can damage the camera if the MC-35 is damaged or the GPS is wired improperly.
This design is for Nikon camera bodies that support the 10 pin remote connection. To date, all Nikon camera bodies that have a 10 pin connector use the exact same pin out definitions. This is likely to be true forever.
The power requirement of the GPS is small but does consume power. PRO bodies’ use a big battery and the GPS unit and camera will be able to go all day with the GPS powered up all the time. It has been found that the GPS unit on a D2x will last all weekend on one charge with the GPS on for the 50 plus hours. The other Nikon bodies that use the smaller consumer batteries will be easily able to go all day on a single charge with the GPS powered up all the time.
There is the option to put a power switch in the design. This author did not do this for several reasons. One is the weather tightness of the construction. The other is GPS signal acquisition. When you start the GPS unit from a cold start, the unit can take nearly one minute to lock. This is not handy or desired by this author. Cold start is defined as unit off for many days or moved 100s of miles between the power cycles. Out of the package from China, the unit takes about 50 seconds to lock the fix. When the unit has been moved but not miles and power cycled, it takes about 10 seconds to lock a fix. If the unit is not moved and the power cycled, the unit locks a fix in less than a second. An add benefit of this unit is that if powered up and the unit has gotten a fix BUT lost the fix, the unit will report the last fix until a new fix is found. This feature is very handy when going inside for a while. The camera records the last fix so you know approximately where the inside images are.
There is another big reason to leave a GPS always powered up. Each cycle of the GPS is a guess of your location. The GPS reports the best answer it has at 1 second intervals. Over time the guess gets better so the actual location is reported with less error. It is like trying to find a square root. It is easy to find out if the answer is right for a square root. Multiple the answer by itself and it should equal the number! If it is not, then the number given is slightly wrong by some amount. The GPS units are doing the same thing but with an equation many times bigger. It guesses your location and then runs the equation. If the answer is not zero, the location is slightly wrong. Additionally, there is but another reason to leave GPS units on. The location of the GPS satellites move. Sometimes the location of the received satellites is poor. The GPS unit can figure this out and compensate somewhat for this. Each satellite tells the GPS unit what satellites it should see in the sky. The GPS actually projects what speed and direction the unit is moving to refine the next guess cycle. At power up, the GPS unit must acquire the satellite clock, lock onto each satellite signal delay, update the satellite location data, and guess its new location, direction and speed. This is a lot to do in a short time and why the fix time varies with what data the GPS already has that is correct. Therefore it is best for quick and accurate “fixes” to leave the GPS unit always powered up.
Power selection is an issue with older cameras. The D2x does not have the new menu item that tells the camera to go into sleep mode if a GPS signal is present. If the GPS signal is present, the D2x is always powered up. The D3s, D3x and D700 have the new GPS menu item. You have two power selection options. One, GPS unit is powered regardless of camera status. This is called battery power. Even if you turn off the camera with the power switch, this power is present at the MC-35 and the GPS unit continues to draw power from the battery and is always ON! The author likes this. The GPS unit is always ready! Want to stop power draw, un-hook the GPS from the camera. The second is meter power. This not the power to the exposure meter but its status follows the status of the exposure meter. It has the states of on or sleep (off). It follows the camera metering system. On a D2x, there is a deadly embrace with meter power or battery power. The camera will not sleep because it sees a GPS signal. If the D3 and the like are set in the default setting for the GPS setting, they act the same way. But if you turn on the GPS sleep setting even with a GPS signal present, the camera meter system sleeps and turns off meter power in the MC-35.
So if use meter power for the GPS unit, it will power down with the meter system. The issue is that the GPS unit is NOT instant on to a fix. So, touch the shutter button to turn on the meter system but you must wait for a GPS fix. It can be up to one minute for a GPS fix. If the meter then goes to sleep in 30 seconds, the GPS unit may not have completed a fix and the COMPLETE FIX CYCLE must be done again. This can be up to 1 minute! The battery power appears to be the best option for most and NOT meter power. You could put in the power selection switch that selects battery power, meter power or off for the GPS unit but why? You can just unplug the unit.
Note that battery power is NOT the actual battery power. It is a regulated supply that runs about 6 volts at the MC-35 that is OK to use with the GPS unit. The meter power is 5 volts.
1. Procure all the components required
2. Take the GPS unit out of the case supplied. Do not damage the micro-connector of the case. You need the micro-connector with 2+ inches of wire for final assembly.
3. Remove the circuit board of the MC-35 with the remote connector intact on the circuit board. The DB-9 connector of the MC-35 is not used for the final assembly and can be cut off at the attachment wires. The camera connecting cable should remain intact. You must “CAREFULLY” cut the MC-35 case to remove the circuit board with the 10 pin connector. The corner of the box must be removed! The top of the 10 pin connector is LARGER than the box hole.
4. Cut the 1551J plastic box for the MC-35 circuit board for the 10 pin connector to protrude out of the box. IT IS VERY EASY to make the hole too big, improperly positioned or the circuit board does not fit! It took two attempts for success for the author! You need to cut a slot for the MC-35 cable to get out of the box. You should be VERY CAREFUL to cut the top of the strain relief off the cable. The box does NOT permit the cable slot to be deep enough for all the strain relief to remain.
5. If you are good, you can connect the micro-connector of the GPS unit without the GPS unit attached. The author could not assure himself of the proper cable lengths so the GPS was put in location for wire attachment. More wire is not a problem but short, you are buying another GPS unit.
6. You can remove the DB-9 connector wires of the MC-35 circuit board. You need three wire connections between the GPS unit and the MC-35 circuit board. They are GROUND (black) [labeled 5 on the MC-35 circuit board], POWER (red) [must connected to the MC-35 cable side of the circuit board, proper location see schematic] and TRANSMIT DATA (green) [labeled 2 on the MC-35 circuit board]. The white wire of the GPS unit is not used.
7. Place all the pieces in the box and epoxy. (See notes)
All the GPS unit wires are very small and easily broken. The author started with 2 feet of wire from the micro-connector and practiced getting the wire ready for soldering. You may need very small gauge insulation tubing if you are not a skillful solder!
The box requires modification to accept the parts. All the screw studs must be removed. None of the included screws of the plastic box are used and can be discarded. The box lid must be refined for the GPS unit to fit. Once you are satisfied that all fits and the lip will close PROPERLY, you can consider step 7.
You should make NO changes to the GPS module as taken out of the plastic holder supplied with the BR-355 package. The outside metal covers protect the electronics from the antenna. Yes, the antenna is bad for the electronics as it sends out harmful RF that should not be seen by the electronics.
Should you wish to verify proper operation, you can place everything wired but not done step 7 on a desk top with a camera and watch the GPS unit come up. You should see the GPS LED cycle from off to solid and then to flash. You should see the camera body go from no GPS symbol to GPS symbol flashing and then to GPS steady. If you do this inside, don’t expect the GPS unit to get a fix! It takes a while for the 1st fix. Don’t get alarmed! Time the cycle so you know what a cold fix takes. It should be 50+ seconds!
The MC-35 circuit board must be shaved just a bit to fit the box. Be VERY CAREFUL not to remove any of the copper tracing of the circuit board.
Orientation of the parts can be done several ways but the author found the box would only accept the GPS unit at one end and the MC-35 at the other end!
You can read on-line how others are doing this and they place the GPS unit with the antenna DOWN. The antenna is the small square piece on top of the bigger base of the GPS unit. You are likely to use the unit with the 10 pin connector up. If you use the GPS unit with the antenna down, it does not work as well. SO, place the GPS unit with the antenna up on the same side as the 10 pin connector coming out the box. If the 10 pin is up, then the GPS antenna is up!
The receiver is the best money can buy right now!
Battery power is 3rd connection from right with the board positioned at shown.
Meter power is the 4th connection from the right with the board positioned at shown.
It easier to just skip the power switch since the box is small.
The white wire of the GPS unit is NOT connected. (Receive Data)
|Parts List: Quantity||Description|
|1||Nikon MC-35 GPS cable ($49.99)|
|1||GlobalSat BR-355 GPS unit PS-2 model no added cable ($34)|
|1||Hammond 1551JBK box ($1.56)|
|1||Toggle switch, three position P/N 35-244-10 ELFA ($1.95)|
GPS Unit Specifications:
•44 channels satellite tracking
•Cold/Warm/Hot start time: 29/10/1 seconds (on average)
•SBAS (WAAS, EGNOS) support
•Superior sensitivity: -160dBm tracking
•Update Rate: 1 Hz
•Support standard NMEA-0183
•Dimension: 3.03 (L) x 1.81 (W) x 0.77 (H) inch
•Weight: 3 oz
Position: <3m 2d-RMS; DGPS: 2.5m
Acceleration: 0.1m/s2; DGPS: 0.05m/s2
•Frequency: L1, 1575.42MHz
•C/A Code: 1.023MHz chip rate
•Antenna (internal): Built-in low noise patch antenna
GlobalSat BR-355 SiRF Star III USB Cable GPS Features
1. SiRF Star III High Performance GPS chipset
2. High sensitivity (Tracking Sensitivity: -159 dBm)
3. Extremely fast TTFF (Time To First Fix) at low signal level
4. Support NMEA 0183 data protocol
5. Built-in SuperCap to reserve system data for rapid satellite acquisition
6. Built-in patch antenna.
7. Super-cohesive magnetic for mounting on the car
8. RS232 interface connection port.
9. Waterproof and non-slip on the bottom.
10. LED indicator for GPS fix or not fix.
LED OFF: Receiver switch off
LED ON: No fix, signal searching
LED Flashing: Position fixed
11. WAAS ENGOS is supported.
The GPS unit was bench tested with a GPS analysis program before the start of the project. It was found the unit achieved location accuracy of 1 meter or less if left on for longer than 5 minutes.
The unit sends GPS sentences of various things. The camera only reads the location sentence with time, longitude, latitude, bearing and altitude. All the other GPS sentences are ignored by the cameras.
The actual current draw of the GPS unit is about 26 milliamperes.
Do you really need the MC-35 cable? Well, it turns out you don’t but from a cost and ease of assembly point of view, it is better. First, where do you get the camera 10 pin mating connector? You could cut off an existing cable. There appears to be no commercial source for these 10 pin connectors either male or female.Second, you do need to add translation or level shifting electronics from the GPS unit to the camera. A $1 circuit can do that but you must then hang all of this in the box somehow. Third and the driver for the author, is the 2nd 10 pin connector of the MC-35. This connector allows the use of ALL the things one can attached directly to the camera port without the MC-35. Nikon’s own GPS-1 does not provide this 2nd port. It does allow remote shutter trip but you must buy a $35 cable for this function since the port is geared to the D90 shutter port. You are close to the cost of the MC-35. Then you are stuck with carrying two shutter releases. One for the 10 pin connector and another for the GPS unit.
The real big advantages of the GPS unit selected are:
o Speed to location fix
o Unit always reports a location fix once it has locked. It may be wrong if you went inside but the image is at least tagged close to where it was taken.
o It is super fast at acquiring a fix if it ever had one in the last few hours. It has this thing called a super capacitor. It acts like a battery so that last fix, satellite data, matrix of all the satellite positions and a projection of where it located is stored. This is a capacitor so that it does not wear out easily but since it has very low internal discharge rate, it can act like a battery. Thus it supports temporary data storage for the unit. It is claimed this data is retained for hours.
o It is the latest in GPS chipset even supporting “WAAS” that allows the unit to address atmospheric issues that commonly trouble a GPS unit.
This construction retains the remote shutter release and ALL the functions of the camera 10 pin connection like dual camera release, camera meter wake-up, external power, image capture via Wi-Fi and computer control of camera.
Pictures and Illustrations: