Yes, I made several custom voltage booster units for people, who seem
happy with them
***
AWESOME!..
I use the ammeter to set my worm to ring gap.. It¡¯s a perfect little device..
?
And
no, I have no financial incentive to say so.. I say so because I love mine and
could never live without..
?
Derek
?
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From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Saturday, December 28, 2019
1:27 PM
To: [email protected]
Subject: Re: [Losmandy_users_io]
Mount power supply...
?
Thanks for asking about my power booster units, Brian.
Yes, I made several custom voltage booster units for people, who seem
happy with them.? They are not a mass production product....just for
either Gemini1 or Gemini2.??
If anyone is interested, let let me know with a private email, and I'll
sell you the fee I have now, or make up a new batch if there is sufficient
interest.? ?I do have two G1 and two G2 units still at home ready to
go.? I use mine all the time on my CG11, G11, and GM8 / GM811 mounts, and
the design has been robust over many years of use.??
Here is a picture of one in use. The voltage is the top display, the
amps on the bottom.? You can see the Gemini1 it is running draws very
little current while tracking a balanced load.? If not tracking, either
parked or at terrestrial setting, the Gemini logic circuits take even less
power.??
The boost from variable input voltage about 12V, up to 17V amplifies
the motor torque by 17/12, about 45%.? This does reduce the issue of motor
stalling.?
Another key element of the voltage booster unit is that it protects the
output polarity going to the Gemini, no matter what you connect as the input
polarity.? It was intended for field use in the dark, so that in case you
plugged in a 12V battery backwards, or somehow mixed up the polarity, it would
always output the correct Gemini polarity.? I think that polarity errors
kill more mounts, Gemini or Synta, etc, easily shorting out the internal
circuits, than any other reason.??
Both types of unit also can take as input any cable having a 5.5/2.5 mm
male input connector.? Any DC polarity will work as the input, from 11V to
15V.? I provide a 5 amp 115V AC/12V DC "brick" for household
power.? ?The Gemini1 units have a dedicated G1 DIN output plug, and
the G2 units have a separate male to male cord that fits the
Gemini2.??
Very best, and happy holidays,
?
On Fri, Dec 27, 2019, 9:04 PM Brian Valente
<bvalente@...>
wrote:
>> ?I
use a power supply that I make for Gemini units.?
Michael just to clarify you offer your Gemini power
supplies for sale as well, right?
?
On Fri, Dec 27, 2019 at 8:45 PM Michael
Herman <mherman346@...> wrote:
Hi Deric,
I agree with you that we should protect our expensive Gemini
units.??
However, each system is driving a different load, do knowing how much
current your gear needs means you should try to measure that.? My data
follows...
If perfectly balanced, the only thing the motors are driving with
current are the torque coming from accelerating the load (scope, cameras, and
counterweights).??
The fuse protects using only a current sense (melting a resistive wire
from the current).? But the current used by a Gemini on the DC motors will
depend also on DC voltage (same power = current x voltage, so if V goes up, I
goes down).
My G11 units typically use under 1.5 amps and usually under 1.2
amps.? That peak current is only observed during a Park, where both motors
are slewing as fast as possible.? Normal Sidereal rate tracking uses under
0.4 amps.??
I drive my Gemini units at 17VDC.? If you are driving
at 12VDC, expect the current to be about 1.5 X as high as what I'm
reporting.? I think that if you use (try) a 3 amp fuse in line with the DC
power input,? it should be fine.? (I did have an old motor start to
go bad and it was drawing 1 amp DC over the other motor during fast slews.)
Definitely use a "surge protector" type of AC
power strip.? That is a must especially if you live near any possible
lightning.? Also unplug your Gemini DC input power when not using the
unit.? ?
The Gemini units are designed intelligently to prevent
damage to themselves or to the motors. If the Gemini senses a motor is drawing
too much DC power, it will show a "Stall" or maybe "Lags"
warning.??
Finally, I use a power supply that I make for Gemini
units.? That has a DC voltage and current monitor, as well as a voltage
pump that changes 12 VDC in to 17 VDC out that then goes to the Gemini.?
The current meter allows me to see anything abnormal: if my system is
unbalanced, or a motor is going awry, or my gears are getting jammed (worm to
ring gear used to be a problem if their spacing was mis-set).?
?
What type of fuse or breaker should I use for short and over current
protection? I have already been party to this before. My AVX mount went up in
smoke after it shorted out and the Lithium battery did a rapid discharge
through the mount. Celestron is replacing it, I dont want this to happen to the
G11. Is their pre built devices or a good schematic for a device? I guess That
I can build one but it has been awhile " a Heathkit Ham radio" Thank
you and Clear skies.
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