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Originally Posted by mswhin63
EQMOD does not require minimum 4V, if that information is on the website then it is incorrect. The mount requires the correct logic conversion whether it is 1.8, 3.3 or 5V. (1.8V is experimental ATM)
EQ5 and 6 mounts require a minimum 4 V to make it work not the other way around.
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The 4V limit comes in when considering the 5V interface of the EQ6 Pro and HEQ5. The USARTs of the mount controllers for these mount types have schmitt trigger Rx inputs and these require a level of 0.8xVcc to trigger. 0.8x5 = 4V and this is why those using 3.3V interface cables have found that they do not work with these mounts even though the normal switching threshold of 5V ttl might lead some folks to believe they would.
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I would check the specs properly on the EQ8 if it is 3.3V then many people have it connected wrong. It may work OK for a period of time but may fail very early voiding any warranty.
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Unlike the earlier mounts the EQ8 and AZ-EQ6GT have been designed with 3.3V signalling interface. However, this interface has been designed to be 5V tolerant in order to maintain compatibility with the synscan handcontrollers. This information comes from synta technical staff and was obtained by Richardo Contreras, the skywatcher dealer for Argentina and Chille who approached me when it became clear there was some confusion over the use of EQDIRs and EQ8s. This info was initially posted to the EQMOD yahoo group and re-posted in the EQ8 topic on this forum (by Robin).
So, there is no inherent danger in using an EQDIR using 5V logic levels with an EQ8 - that is what your handcontroller is doing anyway. 5V EQDIRECTS have been widely used with the AZ-EQ6GT mounts for quite some time now with no problems.
When it comes to warranties you really need to check with your dealer as you may find that some would argue that that plugging anything into it, other than the synscan, invalidates the warranty. If this concerns you, or you have any doubt you could always use PC-Direct mode during the warranty period.
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3.3V is also a high speed logic level so running at 5V will limit the speed of communications as well.
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The mount interface only runs at a fixed low speed (9600 bps), there is absolutely no limit imposed on actual mount communication speed when using 5v signalling compared to 3.3V
Chris.