Show Posts
Pages: 1 ... 3 4 [5] 6 7 ... 27
61  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 08:58:33 pm
I see how you got confused. Notice they are biasing the phototransistor to switch faster rather than act more linearly. I don't know what the purpose of the Olimex circuit is. It's an optically coupled OR-gate that resets the processor for whatever reason I don't know. smiley
62  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 08:43:19 pm
Sorry, but I don't see any difference in the Ebay ckt to mine.  The only thing that I see is that I have a LED and a resistor for the LED on the relay.

Also I don't see (nor have I ever seen) pull-up resisitors on the Inputs.

Not trying negative but I would like to understand.

I attached the opto I am using.

The circuit is pretty hard to see for me and I think there is a mistake in it anyway. It looks like the wire shorting out the relay coil shouldn't be there. Notice where the collector of the phototransistor goes and notice that the emitter is not grounded.

Edited: Sorry, that was poorly worded. I meant notice how the collector on the ebay circuit is wired to 5 V and their emitter goes to the base of the driver transistor as opposed to the way your circuit is wired.

63  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 08:33:55 pm

Ah, much better. No short circuit either.  smiley
64  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 08:28:35 pm
Sorry, but I don't see any difference in the Ebay ckt to mine.  The only thing that I see is that I have a LED and a resistor for the LED on the relay.

Also I don't see (nor have I ever seen) pull-up resisitors on the Inputs.

Not trying negative but I would like to understand.

I attached the opto I am using.

The circuit is pretty hard to see for me and I think there is a mistake in it anyway. It looks like the wire shorting out the relay coil shouldn't be there. Notice where the collector of the phototransistor goes and notice that the emitter is not grounded.
65  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 08:10:34 pm
Hmmm.  Ok CrossRoads you lost me at Tx..  I feel retarded but what Tx are you talking about?

Your node names, T1-T8.
66  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 07:51:12 pm
I don't think so -  just uses names on the nets vs drawing lines all over the place. Easy to follow.
The IN and VCC/5V headers could have been drawn on the left side of the page to show signal flow a little better, is the only change I would have made.

It's not clear to me how any current ever flows in the collector of the phototransistor. It looks like there is a missing resistor.
 

Yep, no current source to be seen for the opto collector to relay npn base connection. That dog won't bark.

Lefty

I was hoping OP would catch it. I gave a couple of hints. It's better when you figure it out for yourself, I think.
67  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 07:42:09 pm
I don't think so -  just uses names on the nets vs drawing lines all over the place. Easy to follow.
The IN and VCC/5V headers could have been drawn on the left side of the page to show signal flow a little better, is the only change I would have made.

It's not clear to me how any current ever flows in the collector of the phototransistor. It looks like there is a missing resistor.
 
68  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 07:15:21 pm
Curious, what is pin 6 on the opto used for?  Should I leave it floating?

You can use it to bias the BE junction by placing a resistor from the base to the emitter and reduce the sensitivity to low level LED light and hence produce a sharper switching action. Normally it is left unconnected.
69  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 02:59:17 pm


I guess I'm blind today.

Looking at what?

It looks like the schematic is incomplete around the opto-isolator.
70  Topics / Product Design / Re: 8 Channel Relay Board - Proofreading on: April 14, 2013, 02:01:57 pm
I guess I'm blind today.
71  Community / Bar Sport / Re: What have you made out of old circuit boards? on: April 14, 2013, 01:38:51 pm
I have not reused old circuit boards.

That's okay! Thanks for checking in.  smiley
72  Community / Bar Sport / Re: What have you made out of old circuit boards? on: April 14, 2013, 01:37:53 pm
While working at a used computer store / electronics recycling depot, I covered a wall in the lobby with 600+ used motherboards.  It was pretty sharp (looking).

Sorry.  No pics...

I'l bet that does look pretty cool!

I made a clock out of an old Mac motherboard that happened to have a convenient mounting hole near the center for the clock mechanism's shaft. Kinda hard to read at first glance.
73  Community / Bar Sport / What have you made out of old circuit boards? on: April 14, 2013, 12:34:17 pm
I am about to refurbish my clipboard by replacing the old rusty clip mechanism with a shiny new one and I was wondering what other people had made from un-needed PCB's?

My clipboard is made from a circuit board that I laid out in the 70's using the old crepe tape and dot on mylar method that didn't pass incoming QC. It was for a 6809-based data acquisition system. The fuse holder on the clip was a bad idea for a pencil holder that I don't intend to add to the refurb. smiley

The inset of the reverse side shows a properly routed "star ground" in the analog section, just for the heck of it since star grounds have bee atopic on this forum. That big 32-pin pattern was for the ADC80 a/d converter. State of the art for the time!  smiley

Has anyone else re-purposed old circuit boards?
74  Topics / Product Design / Re: Creating a finished product on: April 14, 2013, 11:22:38 am
I'm also contemplating using a 3D printer to actually build my enclosures and a few other parts for my product, but still worrying about building materials they use in the affordable printers. Does anybody know if something as tough as MDF can be used in a 3D printer? The shapeways.com samples all look somewhat fragile..  smiley-confuse

Are you contemplating using MDF as the chassis of a 3D printer? Our hackerspace has 3D printers made from plexiglass and from plywood as both are easy to laser cut and are dimensionally stable enough. MDF is very dense and has good dimensional stability and routes good but I haven't seen it used for a printer chassis yet. I guess you could try it.

3D printing with plastic still looks a little wavy on the surfaces to me unless you use a really high grade printer.

Back to MDF, it's easy to machine and can now be powder coated which looks really good. It's pretty dense therefore pretty heavy so that could be a plus or a minus for an enclosure. Worth considering for an enclosure for an electronics project.
75  Using Arduino / Sensors / Re: change two identic I2C address from SHT21 on: April 12, 2013, 02:33:43 pm
Yeah, I guess I could have stated that less bluntly.

Their answer of
"Yes, this approach works."
was in regards to multiplexing by controlling power? Or to preventing the parts from seeing the data line, and thus not having an address to respond to?

To use a separate I/O pin for each data line and common up the clock lines. Presupposes that you are using software I2C.
Pages: 1 ... 3 4 [5] 6 7 ... 27