Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Observatories

Pages: 1 | 2 | (show all)
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Harbor Freight Motor Limit Switches new
      #5450535 - 10/01/12 05:36 PM

Well, it's nearly time to motor the beast of a roof I've built for myself (16 x 24 obs). Electric isn't available quite yet, but will be once I get the 300' of wire trenched (oh boy!)

My initial plan is to use the Harbor Freight Hoist motor that everyone is so fond of (1300/650 lbs version, just in case) along with the cable that was supplied with it to open and close the roof. I'll be mounting the motor above the warm room, running the cable from one end to the other with a couple wraps around the hoist spool in between. There will be a turnbuckle and drawbar spring at each end to keep tension on the line and provide a bit of shock absorbing on start-up.

I'd also planned on using the built in limit switch for the opening direction (a simple wedge shaped piece of wood on the under side of the trusses should work nicely), but that leaves me needing a limit switch for closing. I seem to recall others doing something similar but all of the schematics I've been able to dig up are tied in to automation systems. Sure, that'd be a great upgrade down the road, but for now I'd be happy to have the motor do the grunt work for me while I stand in the warm room.

Does anyone have a simple schematic for adding a limit switch in to the HF hoist? Any particular type of switch recommended?

Thanks in advance.

David


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5462971 - 10/09/12 10:21 PM Attachment (58 downloads)

Hi David,

First off, I know what you mean about the trenching. You can check out my ordeal here!

Let me preface this discussion by saying I really don't recommend taking the internal AC wiring from this (or any) motor and running it all over your observatory. It would be much safer to develop a low voltage circuit for your limit switches and use that to control relays that enable or disable the motor. You can design that in a failsafe manner so that a damaged wire is the same as a hit limit switch and thus disables your drive in that direction. Also, depending on your roof design, you can put both limit switches right at the motor and have appropriate blocks on the moving portion of the roof that engage at the motor rather than elsewhere in your observatory.

You'll find the wiring diagram for that hoist on page 9 of the manual. You can see where the internal limit switch S3 is connected between terminals 7 and 8. Unfortunately, the more I look at this circuit, I don't see a simple way of putting a limit switch in for the opposite direction. If you look at the operating mode for the "S1 down" position, the 120 V line (1) comes in, goes through S3 to the top winding of the motor and through the start cap to the bottom winding of the motor using the other side of the switch. When S1 is in the "up" position, the line comes in and feeds the BOTTOM winding of the motor directly, and feeds the top winding through the jumper at S1 and the capacitor. The capacitor is what's causing the phase shift that causes the motor to turn clockwise or counterclockwise. Unfortunately, there's no equivalent path that lets you insert a switch and break the source power to both coils cleanly. Remember, you have to still allow the motor to run the other way when it's on one limit switch. If you break any of the remaining paths from S1, the motor won't run in either direction. Worse yet, you may energize one coil and not the other. Unfortunately the only way to fix this is to re-wire the hand control (S1) a bit. You're going to need to add an additional wire coming from the hand controller, which generally means replacing the cable. You have to get the contact from the upper right of the switch to go through your limit switch, just like it does on the lower right. That way, the power comes in, goes through the limit and THEN goes to the motor as needed. The attached drawing shows the addition of the extra wire and an S4 for your other limit switch. Now, regardless of which way the switch goes, the line comes in and goes through one or the other limit switch before connecting to any other components.

Hope that helps!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Lord Beowulf]
      #5463442 - 10/10/12 09:13 AM

Thanks for the help Beo. I've actually been thinking about doing away with the hand control and building a nice little wall mounted control box that would house two separate switches/buttons for opening and closing, so I'm not too averse to breaking open the hand box.

The limit switches I had in mind would be positioned exactly like you describe, very close to the motor with the stop blocks mounted in the center on the underside of the roof.

I'm certainly open to the DC relay idea, it's just that I've never done anything like that so I'd be learning from the ground up. Wiring in a couple NC switches is already in my wheelhouse as long as I know where to put them


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5463534 - 10/10/12 10:19 AM

Cool. Then in that case, you should be set to go!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Lord Beowulf]
      #5463540 - 10/10/12 10:22 AM

I think I can make my way from the schematic pretty easily. Thanks much.

Now it's just a matter of finding the proper switches and a nice enclosure to put it all in on the wall. I'm thinking of adding in a a master key switch to prevent the accidental opening/closing of the roof.

I'd prefer some sort of flush mount enclosure, but everything I've found so far is ridiculously expensive for what is essentially a small metal box....


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5463587 - 10/10/12 10:48 AM

If you're handy with a drill or Dremel tool, and have access to the wall to do so, you should be able to use just a standard electrical box and a flat cover that you modify for your application. They make a nice water tight grey PVC box you can get at Home Depot for under $10 if you want to go that way (used them in my piers).

BTW, now that I look at the schematic again, I don't see any reason for the second pole on this switch, unless it's to prevent back EMF from blowing the capacitor when you power off. That does make some sense. Otherwise you could just leave that side connected and use two simple switches (e.g. double-pole light switches) to control the up/down. You'd daisy chain the two switches so that they can't both be ON simultaneously, and one would be open, the other close, and they'd stop on the limits. But like I say, the cap may not survive long if it stays connected all the time.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Lord Beowulf]
      #5463620 - 10/10/12 11:03 AM

Oh, I definitely have access to the wall. It's still rough framing and the electric hasn't even been run yet.

Now that I'm thinking about it, a DPDT momentary toggle switch might make the most sense paired with a master key switch on the 120v line (1). Something like this perhaps...

http://www.surpluscenter.com/item.asp?item=11-3259&catname=electric

Should be easy to mount in a standard wall box and I can get one of those fancy switch covers to prevent accidental bumping.


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5463732 - 10/10/12 12:03 PM

Perhaps a couple of these for the limit switches?

http://www.digikey.com/product-detail/en/V15T16-CZ100A05-K/480-2989-ND/1823501

Or do I leave the existing limit switch in place and just add my own for the opposite direction?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Wmacky
Carpal Tunnel
*****

Reged: 11/24/07

Loc: Florida
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5463794 - 10/10/12 12:50 PM

When to you plan to start? I'd like to do the same as you, and go with cables rather than gears. It seems less complicated. Any chance of you documenting the cable routing, and wiring as you proceed?

Edited by Wmacky (10/10/12 12:56 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Wmacky]
      #5463798 - 10/10/12 12:52 PM

Hopefully I'll be getting started the week of the 22nd when I get the electric trenched and run. I could probably mount the motor and get it all ready before then, but there is plenty to keep me busy in the little free time I have right now

I'll definitely be documenting with photos and such as I go.

My main build thread is located here if you are interested.
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5276997/page/0/view/collapsed/sb/5/o/all/fpart/1


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5463904 - 10/10/12 01:57 PM

Here would be an appropriate limit switch:

http://www.digikey.com/product-detail/en/GLLA01A2B/480-2705-ND/1249040


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Christopher Erickson]
      #5463918 - 10/10/12 02:02 PM

Thanks Chris. Just curious why you chose that particular switch. I'm obviously new to this kind of thing and I love to know what the reasoning behind it is.

Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Lord Beowulf]
      #5464437 - 10/10/12 09:05 PM

Ok, so I think I've worked out a possible setup for my roof motor. I did a bit of editing to the schematic. Let me know if you think I may have mucked things up



Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5464665 - 10/10/12 11:55 PM

Quote:


Now that I'm thinking about it, a DPDT momentary toggle switch might make the most sense paired with a master key switch on the 120v line (1). Something like this perhaps...

http://www.surpluscenter.com/item.asp?item=11-3259&catname=electric

Should be easy to mount in a standard wall box and I can get one of those fancy switch covers to prevent accidental bumping.




Yeah, that'll work, although it's not all that pretty. Works if you're going for a retro look! That's essentially what the rocker in the hand controller is as well. Chances are you'll be able to release that one from the housing and could use it if you want to take the time to make a rectangular hole in your box cover. Not as easy as a circular hole for a toggle switch, though.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5464685 - 10/11/12 12:14 AM

Quote:

Perhaps a couple of these for the limit switches?

http://www.digikey.com/product-detail/en/V15T16-CZ100A05-K/480-2989-ND/1823501

Or do I leave the existing limit switch in place and just add my own for the opposite direction?




Those will work, but there actually a bit small. Given the size of what you're moving and the likely tolerances you're dealing with, I'd go for at least a longer actuator arm, even if you can't find a bigger body. You want to make sure the switch has plenty of travel of the contact roller so that it engages even over a 1/4" gap or more.

As far as the existing limit switch, again, I'm not exactly sure what's there, but I don't think you can use it, although you may be able to leave it and wire in series. My guess is that it's designed to detect when the spool is full or when the hook bottoms out, so since you're never going to have a full spool, it won't do you any good there.

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: Christopher Erickson]
      #5464705 - 10/11/12 12:30 AM

Quote:

Here would be an appropriate limit switch:

http://www.digikey.com/product-detail/en/GLLA01A2B/480-2705-ND/1249040




Definitely a good choice. Pricey, but the adjustable actuator height and long total travel make it pretty versatile. The tradeoff is that there's more variability in where the switch action occurs, relative to the travel distance. If the lever arm is set too long, there will be more potential travel before the circuit breaks. Just something to be aware of when adjusting...

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
Lord Beowulf
Pooh-Bah
*****

Reged: 10/13/08

Loc: Cedar Park, TX
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5464720 - 10/11/12 12:45 AM

Quote:

Ok, so I think I've worked out a possible setup for my roof motor. I did a bit of editing to the schematic. Let me know if you think I may have mucked things up





Everything looks good except the power indicator lamp. You'll need to run the neutral side back over to line 3. As is, you'll be drawing power through the cap and motor windings to try to light it, and assuming it lit at all, it will do interesting things when you actually engage the motor!

Depending on what you find for a keyed switch, you might actually go with a DPDT that can disconnect both the line and neutral of the whole setup, similar to just unplugging the hoist. Either way, I'd just bring the Romex into the box with your switches, catch your line and neutral there for the light, and then route them to the motor from there as needed. Thus 1 & 12 on the terminal block would go completely away and you'd just use 3, 7, 10, and 11 coming from your control box and limits. Don't forget your ground line though!

Beo


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches new [Re: Lord Beowulf]
      #5465013 - 10/11/12 09:15 AM

Quote:

Everything looks good except the power indicator lamp. You'll need to run the neutral side back over to line 3. As is, you'll be drawing power through the cap and motor windings to try to light it, and assuming it lit at all, it will do interesting things when you actually engage the motor!

Depending on what you find for a keyed switch, you might actually go with a DPDT that can disconnect both the line and neutral of the whole setup, similar to just unplugging the hoist. Either way, I'd just bring the Romex into the box with your switches, catch your line and neutral there for the light, and then route them to the motor from there as needed. Thus 1 & 12 on the terminal block would go completely away and you'd just use 3, 7, 10, and 11 coming from your control box and limits. Don't forget your ground line though!

Beo




I was afraid of that bit. I noticed it after I post. I somehow saw that I was going through the cap, but completely missed the motor coil when tracing The idea about running the source power through my junction box got me thinking. I like the idea but may tweak it a bit to just make it a switched outlet that the hoist plugs into. That way, it'll be easier to swap out if it ever fails.

Finding a key switch that I'm confident can handle the load is proving difficult (unless I want to spend $100 just on that bit), so I'll probably skip that novel idea. It would have been nice, just for extra piece of mind, but I'll deal without it

I may stick with the "retro" toggle switches. It'll add a little character to the place, right?

Once again, thanks for all your help on this. I think this is going to turn out nicer than I originally planned.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Harbor Freight Motor Limit Switches new [Re: David81]
      #5467100 - 10/12/12 05:03 PM

Quote:

Thanks Chris. Just curious why you chose that particular switch. I'm obviously new to this kind of thing and I love to know what the reasoning behind it is.




Sorry I didn't see your question sooner. I have been busy preparing to run a bunch of new fiber-optic cables from the focal plane of the UH88 telescope to the comm room below their control room. The cable route is a real maze of cable corridors and plenum spaces and everything must be pre-planned down to the small details.

At any rate, the limit switch I recommended is the standard type used in this type of project. It is robust, sealed and highly-adjustable. It is designed for commercial and industrial electromechanical applications.

I hope this helps.


Post Extras: Print Post   Remind Me!   Notify Moderator  
David81
sage
*****

Reged: 05/17/10

Loc: NE Ohio
Re: Harbor Freight Motor Limit Switches [Re: Christopher Erickson]
      #5467135 - 10/12/12 05:27 PM

Quote:


Sorry I didn't see your question sooner. I have been busy preparing to run a bunch of new fiber-optic cables from the focal plane of the UH88 telescope to the comm room below their control room. The cable route is a real maze of cable corridors and plenum spaces and everything must be pre-planned down to the small details.




You were just looking for an excuse to brag about that beautiful scope, weren't you?

Anyway, that's what I was figuring the reason was, but wanted to make sure. Given that I'd like to not have to mess with this once it's all wired up, that's probably the way I'll go.

Thanks again.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | (show all)


Extra information
7 registered and 5 anonymous users are browsing this forum.

Moderator:  Christopher Erickson 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 2140

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics