Hand Controller

In late 2007 my LX200 developed a problem with the declination drive - this was corrected and the declination encoder board schematic was created while the board was stripped bare. While looking online for documentation for the LX200 I ran across a couple of joysticks that had been used with the LX200, and got to thinking about what the ultimate LX200 Hand Controller would be like. I listed some ideas on MAPUG and got a few more from there also. In order to completely understand the current hand controller, I stripped mine of all parts and created a new schematic for it as well. Being totally anal, I also created the layout of the PCB. I have not yet added the traces, but with the high resolution photographs of the front and back of the board that can be done, sometime when I really have too much time on my hands!

New LX200 Hand Controller
Here are the features I am aiming for with the new hand controller:
    Brighter Map Light
    Joystick control of N-S-E-W
    Switch control of joystick so N will always move the guide star up (other directions corrected too)
    RF or IR wireless link to main scope
    Voice Recognition

As this project possibly moves forward I will update this area to give current information. This is not something I am doing for profit - rather to increase my pleasure using my LX200. All schematics and firmware will be made available at no cost.

UPDATE: January 21, 2008
I replaced the red LED MAP light with a white LED - it is now useable as a light.

I have spent the past 3 weeks capturing data between the LX200 Telescope and the Hand Controller. There are over 200 commands - twice the RS-232 commands listed in the manual. I have complied all the data into a PDF file "LX200 Hand Controller Communications". The first 8 sections cover all the hand controller commands and the response (if any) from the main telescope. The remaining sections cover typical operation of every function of the hand controller, the commands it sends for the occasion and the response from the main telescope.

I am continuing to plan the new controller and have located most of the parts I will be using. More details as I progress will be posted.

UPDATE: January 25, 2008
While working on the LX200 Hand Controller Communications, I had the back of my hand controller off. More than once I would pick up the hand controller only to feel a searing burning coming from the bolt holding the LM340-5 voltage regulator. Doc G even comments on his website of how hot the LM340-5 runs. Well, I have done something about it - I replaced it. The LM340-5 is a wonderful voltage regulator that has been around since the 70's. It will accept input voltages up to 35vdc and give a 1A output. They are cheap and readily available. They feature thermal shut down, which makes them almost indestructible. The drawback is they are a linear regulator. The voltage difference is between the raw input voltage and the output voltage has to be discarded, and is discarded as HEAT. I measured the LM340-5 on my hand controller, and in ambient air of 75°F, the tab on the LM340-5 reached 148°F. No wonder that it kept burning me.

I recently found a switching regulator that is a direct drop in for the LM340-5. Switching regulars are far more efficient than linear regulators. They only let in voltage when they need it. The Murata Power Solutions 78SRH-5/2-C is rated at 95% efficient and rated for 2A output. I purchased mine from Newark Electronics (part number 40M6588). Newark has no minimum order amount and you can order online using a credit card. My unit cost was $13.95 as of January 22, 2008. Here is an image of the new voltage controller installed on the hand controller. Another image of the overall board. The slight overhang does not strop the back of the case from fitting on the hand controller.

I attached an ammeter between my telescope and the hand controller and made the following observations:

                                    LM340-5         78SRH-5/2-C
Powered on, idling            102.6mA            51.9mA
All lights off (Mode 5)    25mA               28.3mA
Backlight at Level 1        25.5mA                28.1mA
Backlight at Level 2        27mA                28.6mA
Backlight at Level 3        29mA                29.0mA
Backlight at Level 4        31.7mA              29.7mA
Backlight at Level 5        35.6mA             30.9mA
Backlight at Level 6        39.5mA             32.9mA
Backlight at Level 7        47.8mA             34.7mA
Backlight at Level 8        55.2mA             37.7mA
Backlight at Level 9        67.2mA             41.3mA
Backlight at Level 10       102.6mA           64.9mA

Backlight at Level 10       120.4mA            57.5mA
with WHITE LED
Map Light

There is no noticeable heat coming from the new 5v regulator.

CAUTION: Replacing the LM340-5 requires disassembling the Hand Controller and soldering on the board. If you are not totally comfortable with this, please find someone who is skilled with a soldering iron to do the job for you. You might could even barter some viewing time for the job.

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