Search found 48 matches

by cosmicray
Sun Jan 04, 2015 10:42 am
Forum: General Chit Chat
Topic: negative voltage
Replies: 5
Views: 1902

Re: negative voltage

Some measured data ... when I short the control line to ground (changes output from 13.6 to 14.2V), the current thru the control line is 22 uA. When I apply a single AA battery to supply -1.5V on the control line (changes output from 13.6 to 14.6V), I measure 44 uA on the control line. Using 2xAA ba...
by cosmicray
Fri Jan 02, 2015 9:01 pm
Forum: General Chit Chat
Topic: negative voltage
Replies: 5
Views: 1902

Re: negative voltage

It's an external 13V-15V battery charger / power source. It comes in a variety of amperage capacities. The internal circuitry has a small jack on the rear, which is used either with a dumb plug (basically shorts one pin to ground) or an optional semi-smart controller. The controller monitors the vol...
by cosmicray
Fri Jan 02, 2015 5:07 pm
Forum: General Chit Chat
Topic: negative voltage
Replies: 5
Views: 1902

Re: negative voltage

Thanks ! I was unaware of the 4051/4052/4053 series of multiplexers. I'm leaning towards using one of the 3 selector lines to choose a value (ground or negative voltage) and using the inhibit pin for when I want the positive (default floating) input.
by cosmicray
Fri Jan 02, 2015 9:56 am
Forum: General Chit Chat
Topic: negative voltage
Replies: 5
Views: 1902

negative voltage

I have a need to drive a control line on an external piece of equipment. After some investigation, I now understand the control signal that I need to generate. There is one wire that needs these values (constant DC, until I want to change state) with respect to ground: high - approximately +2.5 volt...
by cosmicray
Sun Dec 28, 2014 8:53 am
Forum: General Chit Chat
Topic: BusPirate v3 vs BusPirate v4
Replies: 2
Views: 1837

Re: BusPirate v3 vs BusPirate v4

Replying to myself ... I came across this post on eevblog http://www.eevblog.com/forum/beginners/good-cheap-uc-with-low-jitter-usb-hid-capability/msg436685/#msg436685 which led me to this post on dangerousprototypes http://dangerousprototypes.com/forum/viewtopic.php?f=4&t=1169&start=15#p57291 Which ...
by cosmicray
Sun Dec 21, 2014 1:19 pm
Forum: General Chit Chat
Topic: BusPirate v3 vs BusPirate v4
Replies: 2
Views: 1837

BusPirate v3 vs BusPirate v4

I'm going to buy one of these, but the question is which one. The v3.6 seems to be mature, but may be near the limits of what can be done with that board/cpu. The v4 is described as being much more capable, but rough, not quite ready for serious use, and I'm getting the impression that that has been...
by cosmicray
Fri Dec 19, 2014 6:50 am
Forum: General Chit Chat
Topic: Oscilloscope needed
Replies: 13
Views: 2653

Re: Oscilloscope needed

My Hantek DS2090 (20MHz, $100 or so).. has a cable with 2 USB connectors; 2nd one can sum power from a different USB port. But I normally use just one and it's fine. Bought direct from small seller in China. Scope does well for 8MHz and lower signals. Need 3x or 4x signal freqs in bandwidth and sam...
by cosmicray
Thu Dec 18, 2014 6:56 am
Forum: General Chit Chat
Topic: Oscilloscope needed
Replies: 13
Views: 2653

Re: Oscilloscope needed

Yeah, I've got some 210,000 mAh deep cycle golf cart batteries to mess with. They mass a bit more than the unit you're speaking of, but they have more staying power. :D
by cosmicray
Wed Dec 17, 2014 8:02 pm
Forum: General Chit Chat
Topic: Oscilloscope needed
Replies: 13
Views: 2653

Re: Oscilloscope needed

It also just occurred to me, that building my own USB cable, with a Pololu D24V10F5 regulator board, would give me the 5V @ 1A, without impacting the laptop battery (assuming I have a nice 12-13V source handy). Hmmm.
by cosmicray
Wed Dec 17, 2014 3:53 pm
Forum: General Chit Chat
Topic: Oscilloscope needed
Replies: 13
Views: 2653

Re: Oscilloscope needed

One picture is worth a thousand mili-amps. :clap:

Thank you.
by cosmicray
Wed Dec 17, 2014 12:59 pm
Forum: General Chit Chat
Topic: Oscilloscope needed
Replies: 13
Views: 2653

Re: Oscilloscope needed

Beware of Dave's USB scope rants. He did make a favourable one last week though. I have a hantek usb scope (DSO 2090) and it needs to be powered from 2 usb ports. It starts with just 1 plugged in but may not work correctly. So take that into account. That implies that it's drawing more than 500 mA,...
by cosmicray
Wed Dec 17, 2014 7:59 am
Forum: General Chit Chat
Topic: Oscilloscope needed
Replies: 13
Views: 2653

Oscilloscope needed

Hi, I think it's time I invest in an oscilloscope. Picking one is turning into a devil of a choice. From what I can tell, there are two basic styles, one is a conventional desktop model with integrated screen (like Sparkfun sells), the other is a USB style, which uses the PC's screen. It is possible...
by cosmicray
Sun Dec 14, 2014 8:05 am
Forum: General Chit Chat
Topic: ribbon cable for a 4P4C connector ?
Replies: 4
Views: 1603

Re: ribbon cable for a 4P4C connector ?

How long must it be ? For the few pennies extra, you might buy one w/connectors and snip one end off and recrimp to get a custom length or pinout. http://www.homedepot.com/p/Steren-25-ft-4C-Modular-Line-Cord-Black-ST-304-025BK/205317853 That is effectively what I did last night. In my wire box, I f...
by cosmicray
Sat Dec 13, 2014 6:24 pm
Forum: General Chit Chat
Topic: ribbon cable for a 4P4C connector ?
Replies: 4
Views: 1603

Re: ribbon cable for a 4P4C connector ?

The 4P4C connector is the one used between the telephone and the handset. The telephone to the wall is a 6P4C (or RJ-11). Pretty much all of the handset cables I have ever seen are coiled. I need a flat ribbon, not a coiled cable. Although it may be that the cable used in the 6P4C is the same pitch ...
by cosmicray
Sat Dec 13, 2014 4:21 pm
Forum: General Chit Chat
Topic: ribbon cable for a 4P4C connector ?
Replies: 4
Views: 1603

ribbon cable for a 4P4C connector ?

I have a bag of 4P4C connectors, and I need to crimp a few of them onto a length of ribbon cable. I have two kinds of ribbon cable in front of me, one is a 6-conductor/15-foot piece that I purchased from Sparkfun. The other is a 100-foot roll of very old (circa 1973) 25-conductor ribbon cable. The o...