Mach2 Slew Speed, Power, and Voltage Question #Mach2GTO


John Upton
 

Hi Folks,

   I am a new Mach2 owner and am configuring my setup. I usually run completely off battery power whether imaging / observing from home or at a dark sky site.

   My question is: at what input voltage threshold does the Mach2 switch from 1800X slews to 1200X slews?

   My LiFePO4 battery puts out a fairly constant 13.25 +/- 0.25 volts throughout its discharge curve (as much as I use before recharging). I run my at-mount NUC control computer at 19 volts using a DC-DC converter rated at 10 Amps output. I have three choices for running my Mach2. They are:
  1. Run directly from the battery at ~13.3 volts.
  2. Run through a DC-DC converter at 19 volts. (I already have a spare 19 V 8 A converter.)
  3. Run through a DC-DC Converter at 24 volts. (I already have a spare 24 V 10 A converter.)
   My preference would be to use options #1 or #2. I can use option #3 but that converter is physically larger than the 19 V version. I would like to save a little space and weight. (Both DC-DC converters are "fully potted" have hefty heat sinks. Since I always use the battery system for power, every pound matters for travelling, setting up, and tearing down.)

   If there is a fixed threshold at which the Mach2 / CP5 switches from 1200X to 1800X for maximum slew speeds, I can use whichever option for power is most appropriate. If that threshold is lower than 13 volts (unlikely) I could use just the battery and have full slew speed available. If the threshold is less than 19 volts, either of options #2 or #3 should work fine and allow full speed slews at all times. If the threshold is greater than 19 volts, I am left only with option #3.

   Any information regarding the switching point for slowing down slews would help me decide the path forward. (Of course, it may be that there is no fixed threshold and the CP5 simply regulates slew speed on the fly as it needs.) I realize that I "nit-picking" on having 1200X or 1800X available but like weight, saving time can be important.


John


John Upton
 

Hi again,

   Well, I made the decision to go for Option #3 using the 12 volt to 24 volt DC-DC converter. I was sort of forced into the decision after doing quite a bit of testing of Option #1, using the raw battery voltage (~13.3 v).

   I found that running at 13.3 volts, the CP5 control box was very sensitive to voltage fluctuations. If I applied power to the mount first and then turned on the (high end) NUC mount PC, the mount's power LED would immediately turn amber even just sitting at park. I could not slew at full speed either. The CP5 would indicate a motor stall during the high speed slews and show the amber LED again. The voltage fluctuation was short enough to not show up with my digital multimeter and was not detected by the battery monitor I use with the battery. (I did not bother hooking up an oscilloscope to see how long the voltage droop lasts but expect it is very short.)

   So, I installed the 24 volt DC-DC converter. This solved the high speed slew issue and also the voltage fluctuation when powering on the NUC but introduced another issue I will need to solve. My interface to the battery is via a typical automotive 12 volt socket. The plug portion has just enough resistance in the spring loaded tip that it overheats when performing a long slew at 1800X. Doing several long slews in succession, I actually melted part of the plug without blowing the 10 Amp fuse in the plug tip. I will need to rework my battery box to provide a direct PowerPole connection bypassing the 12 v automotive socket to PowerPole pigtail adapter I am using for now.

   The net of all that is that I will use the mount at 24 volts but will need to beef up my battery interface before using 1800X slews. For now, I'll use 1000X until I can wire in a dedicated 24 v PowerPole socket straight to the battery.


John


Kenneth Tan
 

I used these and they work well for me. Comes under various brand names but all look exactly the same. I suspect they are from the same manufacturer. 



On Tue, 30 Mar 2021 at 11:42, John Upton <upton@...> wrote:
Hi again,

   Well, I made the decision to go for Option #3 using the 12 volt to 24 volt DC-DC converter. I was sort of forced into the decision after doing quite a bit of testing of Option #1, using the raw battery voltage (~13.3 v).

   I found that running at 13.3 volts, the CP5 control box was very sensitive to voltage fluctuations. If I applied power to the mount first and then turned on the (high end) NUC mount PC, the mount's power LED would immediately turn amber even just sitting at park. I could not slew at full speed either. The CP5 would indicate a motor stall during the high speed slews and show the amber LED again. The voltage fluctuation was short enough to not show up with my digital multimeter and was not detected by the battery monitor I use with the battery. (I did not bother hooking up an oscilloscope to see how long the voltage droop lasts but expect it is very short.)

   So, I installed the 24 volt DC-DC converter. This solved the high speed slew issue and also the voltage fluctuation when powering on the NUC but introduced another issue I will need to solve. My interface to the battery is via a typical automotive 12 volt socket. The plug portion has just enough resistance in the spring loaded tip that it overheats when performing a long slew at 1800X. Doing several long slews in succession, I actually melted part of the plug without blowing the 10 Amp fuse in the plug tip. I will need to rework my battery box to provide a direct PowerPole connection bypassing the 12 v automotive socket to PowerPole pigtail adapter I am using for now.

   The net of all that is that I will use the mount at 24 volts but will need to beef up my battery interface before using 1800X slews. For now, I'll use 1000X until I can wire in a dedicated 24 v PowerPole socket straight to the battery.


John


Tom Blahovici
 

Hi
BTW, if you are using an Intel NUC, 19V is not necessary. They work just fine at 12V as per specs.
My NUC is an i5 with SSD, and thurnderbird 3 to 10G Base T adapter. It works reliably with no issues.
Might save a little space and battery power.
Tom


Kenneth Tan
 

I find the i5 and i7s power hungry if you are using batteries . Consider the M series processors or a celeron. 

Try the latte panda alpha running win 10 pro
More than adequate . Powers off a usb c PD or if u want a 12 v supply.  Relatively cheap too . 

For those who love to tinker this will work too.... has a aduino and gpio ports




On Tue, 30 Mar 2021 at 12:18, Tom Blahovici <tom.va2fsq@...> wrote:
Hi
BTW, if you are using an Intel NUC, 19V is not necessary. They work just fine at 12V as per specs.
My NUC is an i5 with SSD, and thurnderbird 3 to 10G Base T adapter. It works reliably with no issues.
Might save a little space and battery power.
Tom


Seb@stro
 

Just bought a Minix Neo J50C-4 Max with similar features and performance to the LattePanda Alpha but with Quad-core CPU instead of dual and comes in a case + VESA mount. DDR4 memory and M.2 SATA SSD upgradable. No arduino. 10Watts.


ap@CaptivePhotons.com
 

That’s not necessarily true.  If you browse the specifications at the Intel site, it varies a lot.  Some generations are strictly 19v, some are a mixture of 12-24v, some 12-19v.   It varies by CPU (maybe and kit but it looked more like CPU).

 

The marketing literature is often vague, but Intel publishes the actual requirements.  Here’s an example side by side of two 11th gen models:

 

https://ark.intel.com/content/www/us/en/ark/compare.html?productIds=205038,212519

 

The first is 19 only, the second 12-24.

 

Buy carefully.

 

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Tom Blahovici via groups.io
Sent: Tuesday, March 30, 2021 12:18 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Mach2 Slew Speed, Power, and Voltage Question #Mach2GTO

 

Hi

BTW, if you are using an Intel NUC, 19V is not necessary. They work just fine at 12V as per specs.
My NUC is an i5 with SSD, and thurnderbird 3 to 10G Base T adapter. It works reliably with no issues.
Might save a little space and battery power.
Tom


John Upton
 

Kenneth Tan,

On Mon, Mar 29, 2021 at 11:08 PM, Kenneth Tan wrote:
I used these and they work well for me. Comes under various brand names but all look exactly the same.
   I am already using two similar devices to those you linked. One is the 19v version for the mount-side NUC and the second is the 24 v Version I am using for the Mach2. They were both referred to in my very first post as "potted DC-DC Converters". Both function very well. I have used them before on other projects also which is why I had a few sitting around as spares.

John


John Upton
 

Tom Blahovici,

On Mon, Mar 29, 2021 at 11:18 PM, Tom Blahovici wrote:
BTW, if you are using an Intel NUC, 19V is not necessary. They work just fine at 12V as per specs.
   This is not true of all NUCs. The one I am using specifically specifies that 19 volts +/- 10% (or is it 5%) is required. My NUC came with a 120 Watt power brick and doesn't always boot at 13.3 volts from the battery. Many to most of the older i5 and lower NUCs will run fine from 12 - 19 volts and even state so in the specs. This one does not.

   The main thrust of this thread is about the Mach2 power requirements. Specifically, I was looking for information on how far below the 24 volt specifications you lose the ability to slew at full 1800X sidereal speed. In the end, I find I must use 24 v for other reasons and will continue on that path.

John


John Upton
 

Seb@stro & Kenneth Tan.

   Regarding the suggestions that I need a lower power mount-side computer, I am where I want to be. I am using a NUC10 system with an i7 six core processor. I spec'ed it that way for several reasons. You are right that DSO imaging is not very taxing on a PC. However, there are other imaging methods than just long exposure DSO and some of them require more compute cycles from the CPU.

   I built my mount-side mini-PC to be power efficient in normal use. The NUC is running with 16 GB RAM and 500 GB fast NVMe storage. If I turn it loose, it draws as much as 90+ Watts. However, I use a custom configuration which allows it to run DSO imaging at an average of about 12 W with an average of 15% CPU utilization. I think that compares well to lower end Mini-PCs which run at similar power levels of 8 to 12 W at 50% or higher CPU utilization.

   I have plenty of battery power available to me. As of now with the Mach2, it is about the highest power consumption component of my imaging rig. My testing so far is showing a total power usage of about 35 Watts with the Mach2, cameras, and NUC (running Cartes du Ciel, PHD2, Sequence Generator Pro, APCC Pro, and PixInsight (also with a low power configuration)). Prior to the Mach2, this was running about 24 W with my SkyWatcher mounts so the Mach2 has increased the power draw substantially. (For the benefits, though, the Mach2 is worth that extra current it uses.)

   My last set of changes for my Mach2 addition is to rewire my DIY battery box for direct output to the Mach2 using only Anderson PowerPole connections. I currently use the standard astronomy / automotive 12 v cigarette sockets for all power plugs on the battery. (That was done because I once saw a person at a regional star party whose imaging was shut down due to a failure of a custom PowerPole power cable for his rig. No one else there had a spare PowerPole cable to loan him. Lots of folks had spare cigarette cables to offer. The lesson learned by me is to make up spares of any custom cables or else keep them all standard.)

   I knew that the cigarette plug was the weak link for higher currents. It has served me well but I had never had a need to draw up to 7+ Amps through one before. It was interesting to see the effects of significant overheating inside the plug from the Mach2 high speed slews.

John


Kenneth Tan
 

Most NUCs will run on 12 v but if it drops below that it will Cut off. So better to be higher or if not to get a voltage stabiliser

On Tue, 30 Mar 2021 at 20:57, ap@... <ap@...> wrote:

That’s not necessarily true.  If you browse the specifications at the Intel site, it varies a lot.  Some generations are strictly 19v, some are a mixture of 12-24v, some 12-19v.   It varies by CPU (maybe and kit but it looked more like CPU).

 

The marketing literature is often vague, but Intel publishes the actual requirements.  Here’s an example side by side of two 11th gen models:

 

https://ark.intel.com/content/www/us/en/ark/compare.html?productIds=205038,212519

 

The first is 19 only, the second 12-24.

 

Buy carefully.

 

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Tom Blahovici via groups.io
Sent: Tuesday, March 30, 2021 12:18 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Mach2 Slew Speed, Power, and Voltage Question #Mach2GTO

 

Hi

BTW, if you are using an Intel NUC, 19V is not necessary. They work just fine at 12V as per specs.
My NUC is an i5 with SSD, and thurnderbird 3 to 10G Base T adapter. It works reliably with no issues.
Might save a little space and battery power.
Tom


Seb@stro
 

John,

I am where I want to be. I am using a NUC10 system with an i7 six core processor. I spec'ed it that way for several reasons.

Of course, only you know your requirements.  With such a beast, I suppose you can Live Stack, watch a 4K/60fps movie and play GTA-V while you do planetary imaging... (Does it make coffee ? kidding 😉). To me, apart from low power, size and weight were also a main consideration as it'll be piggybacked on an EdgeHD 8 + small refractor riding the Mach2.

FWIW, the NEO comes with 8GB DDR4 2400MHz (upgradable to 16) and a Quad-core CPU clocked at 1.5 GHz (turbo up to 2.8), 240GB SATA SSD and only cost around $300. But I haven't tried it in the field yet, so real world power consumption is TBD.

Nice battery box BTW.

I am a bit surprised no one from AP answered your original question yet (max slew speed vs input voltage threshold). That would interest me as well. For now anyway, I'll stick with 12V all around as I don't need the ultrafast slewing.

Sébastien

_._,_._,_


michaeljhanson@...
 

Gents,

To answer the prior question, the input voltage threshold for limiting the max slew speed to 1200x is 19.0 volts on the way up, and 18.0 volts on the way down.  Meaning, you're limited to 1200x until the input voltage rises above 19.0,  Once it rises above 19.0, you'll retain 1800x unless the input voltage then drops below 18.0. The 1.0V hysteresis window is to avoid "flickering" back and forth between thresholds.  Realize there will be losses in the power cable, and a (Schottky) diode voltage drop in the unit as well.  So, the input voltage seen by the GTOCP5 will be lower than what is reported at a power supply.  This means a 19.0 volt power source will not quite allow you to get 1800x slew rate.

Regards,
Mike Hanson


John Upton
 

Mike,

   Thank you so much! That seals it then; I will continue to use the 24 volt converter for a dedicated power connection to the Mach2. I can understand the need for the hysteresis although I had not considered that aspect before. Nice touch! Thanks again for the details.

John


Seb@stro
 

Thank you Mike! Much appreciated!

Sébastien 


Greg McCall
 

Mike,
that’s very helpful. It sounds like 20v into GTOCP5 is the min for 1800x
If 24v is the nominal, what is the max voltage?

(context: max charging voltage for a 24v battery)

cheers
Greg


michaeljhanson@...
 

HI Greg,

The limiting factor the the upper end of the voltage range is the threshold at which the transient suppression begins to conduct, which will have a very wide tolerance.  This topic was discussed in the other forum a while back, here:
main@ap-ug.groups.io | Max Voltage Question got Mach2GTO/GTOCP5

The general consensus on that thread seemed to be that having a CP5 powered directly by a battery that is also being charged was discouraged. 

Cheers,
Mike Hanson


Greg McCall
 

I was more hoping by now a more specific answer was available as I've never seen a manufacturer not have an actual specification for their equipment.
Having a 24v system and not allowing for use of a 24v off the shelf battery (with charging) seems to be a poor design.
12v or 24v are usually nominal voltage based historically on a car or truck battery systems. (with an appropriate voltage range for charging and discharging batteries)
Using a mixture of batteries to get close to the voltage is just not practical. 


Roland Christen
 


Having a 24v system and not allowing for use of a 24v off the shelf battery (with charging) seems to be a poor design.
Where did you get this idea? You certainly can use a 24 volt battery with charging to power the Mach2.

Rolando


-----Original Message-----
From: Greg McCall <emailgregnow@...>
To: main@ap-gto.groups.io
Sent: Wed, Mar 31, 2021 8:22 pm
Subject: Re: [ap-gto] Mach2 Slew Speed, Power, and Voltage Question #Mach2GTO

I was more hoping by now a more specific answer was available as I've never seen a manufacturer not have an actual specification for their equipment.
Having a 24v system and not allowing for use of a 24v off the shelf battery (with charging) seems to be a poor design.
12v or 24v are usually nominal voltage based historically on a car or truck battery systems. (with an appropriate voltage range for charging and discharging batteries)
Using a mixture of batteries to get close to the voltage is just not practical. 

--
Roland Christen
Astro-Physics


Greg McCall
 

Rolando,
You don't charge a 24v battery at 24v.
Just checking one battery spec at https://enerdrive.com.au/product/epower-b-tec-24v-100ah-lithium-battery/
It can be 28.8v-29.2v for charging and 27-27.6v as a float voltage 
(that's for a lithium battery, specifically, LiFePO4 often used in astro setups, camping, RV industry)
24v is a nominal voltage with the operating range being 22v to 29v 
While I've not been given a specification for the allowed voltages, the discussion so far has indicated these voltages are not suitable for the Mach2

Contrary to what has been said in this message thread (and a similar thread), are saying I can use a 24v battery on the Mach2 while charging?
I just see no specification and now mixed messages.