Search found 2015 matches

by philba
Sat Apr 18, 2009 6:29 am
Forum: General Discussion
Topic: use of 1/4w resistors to control a dc motor
Replies: 14
Views: 2198

Re: use of 1/4w resistors to control a dc motor

5 ohm/12V > 1/4W. at least make the first resistor 1/2W...

I'll point out the obvious that this is a pretty poor way to control a motor.

The better way is to use PWM. I'd use a microcontroller but it could be done with a 555 timer (though not as nice).
by philba
Wed Apr 15, 2009 8:06 am
Forum: General Discussion
Topic: MOSFET Question
Replies: 12
Views: 1800

Re: MOSFET Question

Sambuchi. Nice page on the MOSFET. One thing though, while Vgs(th) is interesting, you should also point out Rds(on) which usually shows the resistance of the device at specific Vgs values. In the case of the NTD2955, -4.5 yields an Rds of 500 mOhms for a drain current of 2A. This gives you good ind...
by philba
Wed Apr 15, 2009 7:44 am
Forum: General Discussion
Topic: MOSFET Question
Replies: 12
Views: 1800

Re: MOSFET Question

Bob, bwahahaha Mr. Little, why do you focus on "P-chann enhanced MosFet or the NPN Darlington."?? What causes you to see those two as equivalent? I think bob is right, read the thread over again. I'll tell you now, the Darlington costs less than the MOSFET but will cost you more in time, cash and fr...
by philba
Wed Apr 15, 2009 7:35 am
Forum: General Discussion
Topic: Remote Control Specs?
Replies: 19
Views: 2222

Re: Remote Control Specs?

The sloppiness is documented in the receiver datasheets. Look at the TSOP1138's DS http://www.vishay.com/docs/82006/tsop11xx.pdf On page 3 there is a chart titled "Frequency Dependence of Responsivity" (it's debatable that's English...) which shows what the TSOP1138 does with off center modulation. ...
by philba
Sat Apr 11, 2009 10:33 pm
Forum: General Discussion
Topic: Remote Control Signals, Info?
Replies: 20
Views: 2431

Re: Remote Control Signals, Info?

those vishay receivers do the same as the sharp receiver that RS carries. They cost about $1.30 and are about the size of the phototransistor alone.

But, hey, it's your choice...
by philba
Fri Apr 10, 2009 4:02 pm
Forum: General Discussion
Topic: Bi-color and tri-color LEDs...
Replies: 5
Views: 990

Re: Bi-color and tri-color LEDs...

I don't have any specific recommendations for you on LEDs. Maybe others will.

Try using a pingpong ball as a diffuser. cut a hole in it and slip it on the LED.
by philba
Fri Apr 10, 2009 3:58 pm
Forum: General Discussion
Topic: Fluorscent Lighting
Replies: 3
Views: 700

Re: Fluorscent Lighting

Yeah, I did that (and a lot of other terms as well). Basically, this seems to be an area with little info. I think that you can put lower draw bulbs on a given ballast. However, since the electronic ballasts are basically switching power supplies (with a programmed startup voltage spike), I suspect ...
by philba
Fri Apr 10, 2009 10:47 am
Forum: Computer Programming
Topic: Thumb drives and Win98SE
Replies: 15
Views: 2874

Re: Thumb drives and Win98SE

win98 no habla NTFS.
by philba
Fri Apr 10, 2009 10:30 am
Forum: General Discussion
Topic: Fluorscent Lighting
Replies: 3
Views: 700

Fluorscent Lighting

I haven't paid much attention to this area until I started building a UV exposure box. I need about a 10"x10" exposure area. I spent a fair amount of time researching UV bulbs and came up with 4 T5 fluorescent germicidal bulbs (G8T5) as the most cost effective solution (they are < $6 each). T5 lamps...
by philba
Fri Apr 10, 2009 10:17 am
Forum: General Discussion
Topic: Bi-color and tri-color LEDs...
Replies: 5
Views: 990

Re: Bi-color and tri-color LEDs...

Tri and bi LEDs have separate LEDs in a single package. Your lamp case is probably clear. If it was diffuse (sometimes call milky) you would see more mixing. You want to use a diffuser.

What's your application?
by philba
Thu Apr 09, 2009 12:42 pm
Forum: General Discussion
Topic: MOSFET Question
Replies: 12
Views: 1800

Re: MOSFET Question

Your Vgs will vary between 5-Vhi and 5-Vlow (er, Vhi-5 and Vlow-5). It makes sense that some won't turn off, at least fully off. You might want to use an NPN with a pull up to drive the gate so that Vgs goes between 5 and 0. Also, last time I looked SwitcherCAD had a pretty limited set of MOSFET mod...
by philba
Thu Apr 09, 2009 9:51 am
Forum: General Discussion
Topic: Remote Control Signals, Info?
Replies: 20
Views: 2431

Re: Remote Control Signals, Info?

If I were doing an all in one receiver, I'd get 38K and 56K receivers. Probably one of the Vishay TSOPxxxx ones. They are relatively cheap and will respond to all the carriers except 455Khz (B&O is the only one there, iirc). The 38K one will receive 36K and 40K just fine. I'd also use a PT to determ...
by philba
Wed Apr 08, 2009 2:45 pm
Forum: General Discussion
Topic: Remote Control Signals, Info?
Replies: 20
Views: 2431

Re: Remote Control Signals, Info?

Al, I guessed at the part number and mouser had it. No datasheet but here's the mouser page - http://mouser.com/Search/ProductDetail. ... JMfw%3d%3d

Interestingly, it shows rise and fall max as 15 uS. I'm surprised it's so slow.
by philba
Wed Apr 08, 2009 1:20 pm
Forum: General Discussion
Topic: Remote Control Signals, Info?
Replies: 20
Views: 2431

Re: Remote Control Signals, Info?

I'll take a look tonight. I recall that it's obsolete and had a hard time digging up the datasheet on the chinese website.
by philba
Wed Apr 08, 2009 8:10 am
Forum: General Discussion
Topic: Remote Control Signals, Info?
Replies: 20
Views: 2431

Re: Remote Control Signals, Info?

Given that the pulses of a typical IR coding scheme run in the 6-10 modulation cycles range, the shortest pulses will be on order of 200 microseconds. I don't see how a video camera running at 30 fps (i.e. 3.33 mS frames) can possibly pick up enough detail. I've played a fair amount with PTs but it'...