PTGyro Pan/Tilt Single Axis Camera Gimbal Gyro

locally made here in new zealand

The PTGYRO is a single axis gyro for controlling one servo in a camera gimbal.
Based on the ST mems gyro LPY430AL, which has sensors in two axes and a maximum rate of 300 degrees per second, with a 1200 dps option.
The CPU in the PTGYRO is a Microchip 16F688 running at 8 MHz
A connector is on the PTGYRO board, so the Microchip can be programmed in circuit, which requires a Microchip progamming adaptor such as PICKIT3 or K149, and a PC.
Servo power is passed straight through, while the PTGYRO board runs at 3 volts from a LP2981 voltage regulator, so will run with 4.5 volts to 8 volts.
The servo output signal is at 3 volts, which happily runs all the servos tested, but may cause problems for servos at higher voltages. ( the servo may not not detect the control signal )
The PTGYRO uses about  20mA.
Setup of the PTGYRO is done with 4 switches and 4 potentiometers. There is one hidden switch or jumper for programming, and two jumpers for gyro sensitivity.


Switch functions:

1: RC / POT selects whether the PTGYRO is controlled from an external RC signal, or from pot A, and changes the function of pot A

2: GYRO X / Z selects the axis of rotation used. The axes are in line with shortest and longest sides of the box. Changing this while the PTGYRO is running may cause errors, as the different axes may have different average values, and could take a long time to self-correct.

3: TILT / PAN sets the mode of operation. Tilt mode sets the absolute position of the servo, and pan mode is for rate of change of servo position. ( relative position )

4: SLOW / FAST sets the servo signal update rate. Slow is standard for analog servos. Fast gives three times faster updates. 1500uS servos only.

5: Used for programming. Leave on.

Pot functions:

A:

Pot A "POSITION" sets the absolute, or resting position of the servo, when switch 1 is set to POT.
In RC input, tilt mode, pot A sets the speed of change of servo position.
In RC input pan mode, pot A trims the stick center.

B:

Pot B "GAIN" sets the amount of effect the gyro has on servo position, and the direction.
If the pot is set to 50%, there will be no effect.

C:

Pot C "TRAVEL" sets the servos maximum travel either side of 1500uS center. Care needs to be taken with this control, as the maximum setting is beyond the limits of most servos.
Servos sometimes growl if they try to go beyond their limits. If you hear that, then turn the travel limit back a bit. If you use a current limited power supply when setting the travel limit, you are less likely to damage the servo. You have been warned!
The travel range is probably best set using the PTGYRO in RC input pan mode, so the servo can be driven to the ends.

Please Note: in tilt mode, the servo may travel further than expected, as the servo position will be set position plus gyro effect.

D:

Pot D "RETURN" controls how the servo returns to the set position, after the gyro has sensed rotation. There are two modes, with the pot either side of 50%. Set to 0% turns the return rate to 0, and may cause the servo to drift slowly to one end of its travel, but may give the most locked-in effect. Between 0% and 50% gives a linear rate of correction. Above 50% is "rubber band" mode, where the further the gyro has moved the servo from its set position, the quicker it comes back.
Operation:
When powering up the PTGYRO, it needs to work out what voltage from the gyro represents not turning, or average value. About one second after power-up, it will perform a series of measurements. It is important that the gyro is not moving during that time. All going well, it will begin working after 4 seconds from power-up. Because of changes in temperature and voltage, the average value needs to be corrected every now and then. Sometimes the correction is wrong, because of high amounts of gyro activity, or the gyro has been turning for a while, such as in an aircraft flying in circles.

Please Note: The switches and pots are delicate, and need to be changed carefully so it is recommended that a Small flat blade jewellers screw drivers are used for changing the switches, and tweaking the pots.

The plastic case of the PTGYRO can be opened with a single screw in the center.
There is a gap under the board, so it could be mounted with screws through the back of the case.
Easy solder pads allow for shortening of the cables if desired ( soldering skills required )
If it is operated outside the case, then make sure the board is insulated, and nothing can short out pins or tracks. Use Heatshrink, or foam tape.