Search found 39 matches

by EPA III
Sat Mar 07, 2009 11:37 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

OK, you come out serial and then what? Feed the serial data to an SR and latch the parallel data into the LEDs. Simple, really. So the serial data would be in seven segment code at the uc output? Do you know of some real cheap LED display (four digit at least and nice BIG numbers like 1/2 inch) tha...
by EPA III
Sat Mar 07, 2009 11:25 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

I said "rotary". I meant thumwheel switch. About $5 and it is the only component you need. Seems to make sense to me. Okay. But why the red ink?... Quotes within quotes within quotes. I thought the red color would make it easier to read: easier to tell what I was saying in the latest reply. Not an ...
by EPA III
Thu Mar 05, 2009 7:44 am
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

A BCD rotary switch should provide the range selection I need with only two or at most three INs. BCD? Why? Wouldn't a rotary digital pot and human feedback from the existing readout LCD/LED suffice? Turn pot up or down, fix value by hitting 'enter' button adjacent to the pot. Or, use a digital enc...
by EPA III
Tue Mar 03, 2009 10:31 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

Thanks guys for starting the thought process. I made a parts list for my original tach circuit and priced it today and was surprised to find that my cheap solution was not that cheap. It came to about $40. I was hoping for $20 or less. So I started to sketch a generic circuit with a uC and was again...
by EPA III
Sun Mar 01, 2009 11:08 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

My overall project is a manual controller for two or perhaps three stepper motors that will automate a small milling machine. It will have provision for future computer control, but for now, I want to get the manual control working well first. The tach circuit will be to display the speed of the mov...
by EPA III
Sat Feb 28, 2009 3:50 pm
Forum: General Discussion
Topic: quick logic level question
Replies: 7
Views: 1772

Re: quick logic level question

The best answer to this may depend on what you are doing with the signal after "converting" it. If you are going into a 3.3 Volt logic chip, a resistor dividing network may work just fine. As a further precaution you may want to add a diode between the 3.3 Volt input and the 3.3Volt supply to preven...
by EPA III
Sat Feb 28, 2009 3:33 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

If you have a better way to make a quick and dirty counter, I am all ears. The simple answer is to add a microcontroller (uC) to your project. Costs about one eighth of the MM74C926, based on Digikey pricing. I have been experimenting with some uCs and I did think of that. But then you have to inte...
by EPA III
Fri Feb 27, 2009 11:46 pm
Forum: Robotics
Topic: stepper motor Help
Replies: 1
Views: 3016

Re: stepper motor Help

Steppers are generally one of two types: unipolar and bipolar. The unipolar will usually have six wires. They will be connected to two center tapped coils and should have enough resistance to allow figuring them out with a regular Ohm meter. Each end to the center tap will have the same resistance a...
by EPA III
Fri Feb 27, 2009 11:19 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Re: Help With Spec Sheet: MM74C926

Thanks! Yes, it is a bit old, but still available. So is the 741 which is a lot older: at least 40 years and that is a lot before Reagan was in the White House.

If you have a better way to make a quick and dirty counter, I am all ears.
by EPA III
Fri Feb 27, 2009 6:16 pm
Forum: General Discussion
Topic: Mass wire storage solutions
Replies: 11
Views: 3775

Re: Mass wire storage solutions

I have a similar problem at work. I use cardboard bins and inexpensive (not cheap) metal shelves. The bins are available in a variety of widths and are relatively inexpensive. I have some cardboard bins that are over 25 years old do they do last. They have nice white areas on the front for labels an...
by EPA III
Fri Feb 27, 2009 6:06 pm
Forum: General Discussion
Topic: Help With Spec Sheet: MM74C926
Replies: 20
Views: 6203

Help With Spec Sheet: MM74C926

I am looking at using a Fairchild MM74C926 to implement a counter circuit for use as a tach. for a stepper motor. The Fairchild spec sheet shows a number of waveform times for operating the IC, but the thing I am confused about is that all the minimum values are larger than the typical values. The m...
by EPA III
Tue Oct 11, 2005 12:41 pm
Forum: General Discussion
Topic: I am claiming dunce of the week
Replies: 44
Views: 10581

Re: I am claiming dunce of the week

jwax said,<p>"I was USAF, repairing shot up planes in Vietnam, when (I hear it happens to everybody-once!) after soldering 128 wires on the back of a big ass Cannon connector, discover I forgot to put the locking ring over the wires before soldering. De-solder 128 wires, curse, add ring, solder 128 ...
by EPA III
Fri Oct 07, 2005 11:09 am
Forum: General Discussion
Topic: AC line / UPS power switch
Replies: 15
Views: 3321

Re: AC line / UPS power switch

It wouldn't be hard to make such a switch. Buy a couple of extension cords, a three way switch, and a small box to put it in. There are plastic boxes available in hardware stores that would look OK on or under the table. For table top use you can cut any mounting ears off. Be sure to get the three c...
by EPA III
Fri Sep 30, 2005 7:15 pm
Forum: General Discussion
Topic: electric motor question
Replies: 12
Views: 2600

Re: electric motor question

Slow down. You really should not have to rewire the garage. <p>Any motor that is designed for dual voltage operation simply has windings that are wound in two sections. Each section needs 115 Volts. When they are in series, the line Voltage is 230. When they are in parallel, it is 115. In either cas...
by EPA III
Fri Sep 30, 2005 6:57 pm
Forum: General Discussion
Topic: Variable PS Design
Replies: 16
Views: 3738

Re: Variable PS Design

Thanks guys! <p>RE: Linear vs Switcher. Yes, I know from experience. 33V (you need a little headroom) - 0.001V times 3 Amps = 100 Watts. That's a small room heater. If you do the research on heat sinks, you find that a switcher is real attractive. I'm not committed to it, but it is most likely a nec...