Hi,
So many of you by now have seen me mentioning hand controllers for the AstroEQ. Supported with the release of the V8.0 Beta firmware, and using the hardware added in the V4.6 AstroEQs, I am in the process of developing two different hand controllers to allow the AstroEQ to be used without a PC connection.
The first of these, and the only one currently developed, is the Basic hand controller. The idea behind this design is to allow very simply control over the AstroEQ when you don't need the full go-to capabilities. This will allow you to drive the mount in a completely standalone fashion with no PC connection needed at all. It consists of four push buttons for NESW, and a fifth button to select between one of three different speeds (ST-4 speed, 2x speed, and GoTo speed).
I have just finished building the first prototype, a photo of which is below. I am making use of a 5-button key fob style case as they are very cheap (£2 each) and already have five nice conductive rubber push buttons. To facilitate the three speed selections, inside the fob there is actually a small 6-pin microcontroller (ATTiny10) which is powered entirely from the pull-up resistors on the ST-4 lines meaning that no external power supply is needed.
The MCU (the software for which is with a whopping 82 bytes!) is required to allow the fifth push button to select between three different speed states by driving the control pin in a specific way - shorting to GND is one speed, connecting to GND via a 2k resistor is a second, and floating the control line a third. A low voltage LED in series with the control line allows for an indication of speed based on how bright the LED is.
It is also possible to build your own version, however I would not recommend the fob case as the circuitry requires quite a few very tiny SMD parts.
Instead I would recommend using simple tactile switches and a slide switch for speed. Below is a schematic of the simpler version of the hand controller. The only parts required are 4x tactile switches (push buttons) of your choice, 4x 10nF capacitors for debouncing, 1x 3.9kOhm resistor, and 1x SP3T slide switch (or similar).
The speed selection switch selects (from left to right in the diagram): ST-4 speed, 2x speed, and Go-To speed.
In terms of functionality, the four push buttons are used to select the direction (you can press an RA and DEC button at the same time) and the slide switch selects the speed. When the switch selects ST-4 speed or 2x speed, the mount will also be set to do Sidereal Tracking. When you select the Go-To speed, the mount will not perform any sidereal tracking.
The speed modes were chosen so that if you unplug the hand controller, the mount will stop moving because the speed pin will float.
Additionally, when doing Sidereal Tracking, the speeds are relative to the sidereal rate. For example at 2x speed, the mount will move 2x speed in DEC+ and DEC- directions, 1x speed in the RA- direction, and 3x speed in the RA+ direction. In other words, the speeds are the rate at which the stars move, not the mount.
When the hand controller is first plugged in, you must select ST-4 speed in order for it to be detected - selecting any other speed will not force the AstroEQ into standalone mode.
The basic hand controller requires the V8.0 beta firmware, and also an AstroEQ with a V4.6 hardware revision. If you have a V4.5 or V4.4 mount, it will be possible to add support however it will require a simple hardware modification. I will write up details on the required hardware modification in a tutorial.
I will publish a tutorial at a later date on the basic hand controller design and operation. In the mean time, if you need any clarification, please post in this thread.
I hope this will be a welcome addition to the AstroEQ controller - I know a few of you have been missing this most basic of functionality.
Kind Regards,
Tom.
