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Forum: 70. Control Systems Tue 18 September 2012, 11:34
Replies: 333
Views: 342,465
Posted By Richards
I've been playing around with a generic schematic...

I've been playing around with a generic schematic for proximity sensors that would allow the use of (mixed) NPN or PNP proximity sensors and would allow you to select N/O or N/C for each sensor. The...
Forum: 70. Control Systems Wed 01 August 2012, 07:50
Replies: 333
Views: 342,465
Posted By Richards
With the relay off, measure the resistance of the...

With the relay off, measure the resistance of the relay's coil. Divide the voltage by the resistance to find the amps needed to turn on the relay. Example: 24V / 1000 ohms = 0.024 Amps and 0.024 X...
Forum: 70. Control Systems Mon 30 July 2012, 15:48
Replies: 333
Views: 342,465
Posted By Richards
The coils on relays require a minimum current to...

The coils on relays require a minimum current to activate the coil. Verify that the proximity sensor can deliver that amount of current.
Forum: 70. Control Systems Tue 03 April 2012, 18:14
Replies: 333
Views: 342,465
Posted By Richards
Everything depends on the way that you use...

Everything depends on the way that you use sensors. When a Normally Open sensor "senses" metal, it closes and when it "senses a hole in the metal, it opens. So, on the MechMate, we could say that in...
Forum: 70. Control Systems Sun 19 June 2011, 15:43
Replies: 333
Views: 342,465
Posted By Richards
Sorry, guys. My Shopbot had targets. Your...

Sorry, guys. My Shopbot had targets. Your MechMates have holes. The designs are opposites. The 74LS32 chip uses "OR" logic which is opposite to the 74LS08's "AND" logic.

I replaced that design...
Forum: 70. Control Systems Tue 27 July 2010, 08:03
Replies: 333
Views: 342,465
Posted By Richards
Pablo, I'm comfortable with the 74HCT logic...

Pablo,

I'm comfortable with the 74HCT logic family as the replacement for the CMOS part. The HCT series has the best of both the CMOS and the TTL worlds. It is used to bridge logic families so...
Forum: 70. Control Systems Mon 26 July 2010, 10:17
Replies: 333
Views: 342,465
Posted By Richards
Pablo, I like your design. It's clean and...

Pablo,

I like your design. It's clean and efficient. So far, the only issue I have is using a CMOS chip to drive (I assume) a TTL chip. Traditional CMOS might have a problem with TTL. To get...
Forum: 70. Control Systems Sun 04 July 2010, 07:35
Replies: 333
Views: 342,465
Posted By Richards
Steve, AC proximity sensors are slow. Those...

Steve,

AC proximity sensors are slow. Those that you specified are rated at 12Hz, which is 83 milliseconds. The DC proximity sensors are rated at 1000Hz, which is one millisecond. The DC...
Forum: 70. Control Systems Thu 27 May 2010, 22:41
Replies: 333
Views: 342,465
Posted By Richards
Sometimes we have to decide whether a proximity...

Sometimes we have to decide whether a proximity sensor that can't sense aluminum at standard distances is better than adding a target that can be sensed (at standard distances).

The design of the...
Forum: 70. Control Systems Mon 29 March 2010, 07:45
Replies: 333
Views: 342,465
Posted By Richards
If you have trouble sensing aluminum, just...

If you have trouble sensing aluminum, just replace the 'hole' in the aluminum with a steel bolt, then instead of sensing the absence of metal, you will sense the presence of metal when you hit the...
Forum: 70. Control Systems Tue 05 May 2009, 10:02
Replies: 333
Views: 342,465
Posted By Richards
Keith, Thanks for the information. Figure 1 on...

Keith,
Thanks for the information. Figure 1 on page 11 is a classic circuit that I've often used. It uses a simple 7400 NAND chip (which is the chip upon which most TTL logic is based). The 7400...
Forum: 70. Control Systems Mon 04 May 2009, 17:20
Replies: 333
Views: 342,465
Posted By Richards
Gerald, I'm going to learn more about Mach 3....

Gerald,
I'm going to learn more about Mach 3. I promise :). It has so many possibilities that will reward those who spend a little time studying.

Keith,
The problem with all electronics is...
Forum: 70. Control Systems Mon 04 May 2009, 11:47
Replies: 333
Views: 342,465
Posted By Richards
I think that we're getting goals mixed up. The...

I think that we're getting goals mixed up. The way I see it, there are three different 'goals':

1. Emergency Stop

2. Mechanical limit

3. Homing

An Emergency Stop (E-Stop) switch needs to...
Forum: 70. Control Systems Thu 01 January 2009, 09:31
Replies: 333
Views: 342,465
Posted By Richards
The standard distance for iron/steel for most...

The standard distance for iron/steel for most flush/shielded 18mm sensors is 5mm instead of the standard 2mm for 12mm shielded sensors. Unshielded/non-flush sensors have 2X the sensing distance. ...
Forum: 70. Control Systems Wed 31 December 2008, 17:24
Replies: 333
Views: 342,465
Posted By Richards
During the last few days, I've been playing with...

During the last few days, I've been playing with proximity sensors again. Much to my chagrin, most of what I've been experimenting with has already been discussed here in the forum. What's worse,...
Forum: 70. Control Systems Fri 30 May 2008, 07:32
Replies: 333
Views: 342,465
Posted By Richards
The opto devices will work, BUT, as always there...

The opto devices will work, BUT, as always there may be a problem.

As you can see, the device is built in a "U" shape. On one side of the "U" is the infared LED, on the other side of the "U" is...
Forum: 70. Control Systems Sun 18 May 2008, 00:15
Replies: 333
Views: 342,465
Posted By Richards
I may have mislead when I gave the $10 figure. ...

I may have mislead when I gave the $10 figure. The $10 is for the glue chip and the proto board. It does not include the limit switches/proximity sensors. The proximity sensors that I use cost...
Forum: 70. Control Systems Fri 16 May 2008, 19:58
Replies: 333
Views: 342,465
Posted By Richards
It looks like we're making this much too...

It looks like we're making this much too difficult. Look at the 7408 chip and the 7430 chip to see how many inputs can be combined to make one official input. Typically, all the limit switches can...
Forum: 70. Control Systems Thu 15 May 2008, 06:36
Replies: 333
Views: 342,465
Posted By Richards
I'm only using Mach 3 on the test bench, not on...

I'm only using Mach 3 on the test bench, not on my machine, so I'm not fully aware of the day to day sequence of events that you use when starting up your machines; however, on my machine, I manually...
Forum: 70. Control Systems Fri 07 March 2008, 05:58
Replies: 333
Views: 342,465
Posted By Richards
Looking back at post #70 where Gerald posted a...

Looking back at post #70 where Gerald posted a drawing that showed various input devices connected to a box as well as an output connection going to the control box, we still need to define the STATE...
Forum: 70. Control Systems Wed 05 March 2008, 11:45
Replies: 333
Views: 342,465
Posted By Richards
Gerald, What you've posted is a classic...

Gerald,

What you've posted is a classic multiplexer/demultiplexer, which is just another name for 'switch box'. The next thing that we'll need is a chart that lists each device and its...
Forum: 70. Control Systems Mon 18 February 2008, 07:26
Replies: 333
Views: 342,465
Posted By Richards
Gerald, Sorry. I should have remembered that...

Gerald,
Sorry. I should have remembered that the sensors are actually going 'active' when they sense the 'hole', which, as you pointed out, makes Sean's circuit work perfectly.
Forum: 70. Control Systems Mon 18 February 2008, 06:31
Replies: 333
Views: 342,465
Posted By Richards
Sean, Those proximity switches must be Normally...

Sean,
Those proximity switches must be Normally Closed for your circuit to work, otherwise you'll only get a 'contact' signal when all three sensors fault at the same time.
Forum: 70. Control Systems Wed 06 February 2008, 12:31
Replies: 333
Views: 342,465
Posted By Richards
Gerald, What you've described should be...

Gerald,

What you've described should be fairly simple to construct, but, we'll need some more information.

PMDX:
How many signals to the PMDX and what polarity (active High or active Low)?...
Forum: 70. Control Systems Tue 05 February 2008, 06:39
Replies: 333
Views: 342,465
Posted By Richards
Gerald, Normally, I build everything around a...

Gerald,
Normally, I build everything around a little 20-pin microcontroller so that features can be added with software - instead of a hardware redesign. The limitation of using a microcontroller...
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