ADVANCED uSTEP
ELECTRICAL INTERFACES

This diagram shows how to connect a hardware generated index pulse from the rotation of the worm to the INDEX connector on the Advanced Microstep Drive Box. The drive box detects the low going edge and generates a :P# event to the Handset. With version 1.4 (or later) handset software this then synchronises the periodic error calibration with the rotation of the worm. The pulse can be generated by a slotted opto-coupler; a magnetic and sensor (with pulse shaping electronics as on the Intes Micro Alter D6 or the Meade LX200) or other type. It can be placed on any axle with a periodic error (for friction drives the major component can be cancelled). FURTHER DETAILS

TEST the interface (see below). External circuit (user circuit) is to the left of the vertical bar.

Three relays are provided which are activated by buttons U1 U2 U3 on the Intelligent Handset. These are single pole with normally closed and normally open connections. They contacts are rated at no more than 1 amp when closed or 50 volts when open. Thus they CANNOT SWITCH MAINS but are useful for a variety of applications. 9 pins are used on the 15 way AUX connector for this use.
With computer control directed through the Intelligent Handset each of the relays can be controlled by use of the :Fab# command where 'a' is the relay number 0,1,2 and 'b' is either 0 for off or 1 for on.

TEST the interface (see below). External circuit (user circuit) is to the left of the vertical bar.

Typical uses would be for:

• Remote FOCUS control which needs a DC motor to drive in and out (2 relays and U buttons)
• Dome ROTATION manual motor control (2 relays and U buttons)
• DEW Heater ON/OFF (1 relay and U button)
• FAN blower control for primary temperature stabilisatio (1 relay and U button)
• AUTO DRIVE SHUTOFF after a pre-determined delay (1 relay and U button)
• FILTER WHEEL advance one position (1 relay and U button)

This pair of wires from the 15 pin AUX connector provides a means of stopping the drive by mechanical sensors closing a circuit. The Telescope STOPS when the circuit is made by microswitches or operator switch on a control panel. If you arrange microswitches around the dome / mount where the tube can bump into then they can serve the right purpose to prevent driving into the object. The control push button is required to start the telescope again by user intervention to drive it away from the obstruction. This OPENS the circuit to put the drivebox into RUN mode.
For the computer literati the override action generates a :Sa# event where 'a' is 0 for released and 1 for active.

TEST the interface (see below). External circuit (user circuit) is to the left of the vertical bar.

You can wire it up with a relay controlled from the U1-U3 buttons. Then you can insert a long delay when the scope would automatically stop driving using the TIMED DELAY method for the User button setup.

If you have assembled the interface yourself then check it before putting on the power. Then power up the drive box. If all is well then you have control over the drive box as normal and you have power available at the connector. To test that the circuit works it must be stimulated and the response checked.

The USER buttons U1, U2, U3 provide the stimulus for the relays and you can hear the relays click, So you need to check that the relay closure is doing something to your external circuit.

The other two functions require a computer connected to the Intelligent Handset by means of the special serial lead in order to check them out. Assuming you have the lead and you have checked that you can acquire the telescope with a planetarium programme then you stand a fair chance of getting the next bit right. The events that are generated can only be checked by seeing the characters on the computer screen as the external circuit is stimulated. The computer must run a 'terminal programme' which allows direwct access to one of the serial comms ports. Our programme, WINDISP is recommended with the correct CONFIG file. It must be set up to write 'direct to the comm port' with the correct serial parameter settings: 9600 baud, 8 data bits, no parity, hardware flow control. Further, the characters you type must appear locally so tick this setting. To check you have a link established then type :GR# and back will come the RA position on the screen. Check that the IH is set to run AWR protocols (FACTORY - COMMS to AWR mode). Now move the slot through the opto-coupler and you should ses the :P# event. If you see this then all is well. Similarly when operating the OVERRIDE circuit you should get the :S1# event.

You can use the same method to interrogate the drivebox directly making use of the Microstep Protocol document. You will need the correct SERIAL interface lead either for the Drivebox or the Intelligent Handset, both are non-standard.

In the event of any difficulty you can contact AWR preferably by email initially describing the problem, what you have done and what you are trying to do.

© 2005-8 AWR Technology