Search found 2781 matches

by haklesup
Thu Aug 21, 2003 1:45 pm
Forum: General Discussion
Topic: Bipolar Transistor Cookbook
Replies: 1
Views: 1159

Re: Bipolar Transistor Cookbook

Conventional Current goes from pos to neg. We use this convention in the majority of engineering calculations with few exceptions.<p>Electron current goes from neg (the source of the electrons - the electrode) to positive (the anode). You can use it this way but you'll need to invert all your answer...
by haklesup
Thu Aug 21, 2003 1:34 pm
Forum: General Discussion
Topic: Diode Voltage multipliers
Replies: 10
Views: 2767

Re: Diode Voltage multipliers

Simply put, there is no getting around the law of conservation of energy and Ohms law.<p>Pin=Pout P=IV (ok, not preciisly ohms law V=IR but derived from it and the power law P=I^2R) <p>So, I*V in = I*V out regardless of the technology you use in between. <p>The only area you have flexibility is effi...
by haklesup
Wed Aug 13, 2003 12:05 pm
Forum: General Discussion
Topic: Best AM Broadcast band Radio for dx?
Replies: 10
Views: 6800

Re: Best AM Broadcast band Radio for dx?

If your shopping for a new radio and the specs are available, you could look at the AM tuner sensitivity spec but the antenna advice is really the best.<p>A quick search on google using "replacing AM antenna" yeilded some articles on modifying the ferrite rod antenna to have a homemade loop antenna ...
by haklesup
Tue Aug 12, 2003 8:17 pm
Forum: General Discussion
Topic: Electrolytic Caps desoldering motherboard
Replies: 5
Views: 2792

Re: Electrolytic Caps desoldering motherboard

Just a little background info:<p>Those caps (and almost all caps on a motherboard) are used primarily for filtering transient noise out of the power supply voltage. These transients are primarily caused by rapid shifts in the demand for supply current as the CPU changes from task to task although so...
by haklesup
Tue Aug 12, 2003 1:38 pm
Forum: General Discussion
Topic: Electrolytic Caps desoldering motherboard
Replies: 5
Views: 2792

Re: Electrolytic Caps desoldering motherboard

There is no trick to desoldering a multi layer board, you just need to be careful not to damage the trace or pad when working on it.<p>Don't heat the connection too long or too hot. This will weaken the substrate. The hot tip of a soldering iron should never be used as a chisel to bend the leads up....
by haklesup
Mon Aug 11, 2003 12:50 pm
Forum: General Discussion
Topic: surface mount LED
Replies: 4
Views: 954

Re: surface mount LED

I've soldered many fine pitch SMT devices by hand, several things come to mind.<p>I find bulk soldering of many pins at a time using flux/solder paste to be a messy disaster if you do not have the proper IR or forced air reflow systems available. Pin by pin hand soldering is more reliable on any par...
by haklesup
Mon Aug 11, 2003 12:13 pm
Forum: General Discussion
Topic: JFET differences: GP vs. SW vs. VHF vs. UHF
Replies: 5
Views: 1060

Re: JFET differences: GP vs. SW vs. VHF vs. UHF

In that case, don't even mess around with discrete transistors. Since you are basically trying to make a 3pdt switch solid state you should use a switch like the DG411/DG412 or the MAX313/314 (quad SPST) or the MAX4661 (lower on resistance). <p>Similarly numbered Maxim (www.maximic.com) chips have o...
by haklesup
Sat Aug 09, 2003 10:02 pm
Forum: General Discussion
Topic: JFET differences: GP vs. SW vs. VHF vs. UHF
Replies: 5
Views: 1060

Re: JFET differences: GP vs. SW vs. VHF vs. UHF

UHF and VHF transistors are designed to operate at higher frequencies with respect to a number of specific specifications. See a data sheet for all those graphs that have frequency on the X axis. Specific methods of construction and design influence the suitability of a device to be in this category...
by haklesup
Sat Aug 09, 2003 9:25 pm
Forum: General Discussion
Topic: MOSFETS II
Replies: 9
Views: 1590

Re: MOSFETS II

Check to make sure no current can flow into the gate terminal. Unless you know there is some kind of diode protection on the gate, any current flowing indicates gate oxide punch through which will often render a FET permenantly on or off (Depending on type and extent of damage). <p>What FET are you ...
by haklesup
Thu Aug 07, 2003 3:37 pm
Forum: General Discussion
Topic: This should be a simple timer circuit
Replies: 7
Views: 1018

Re: This should be a simple timer circuit

As drawn the set and reset are positive and the output goes to 12V when set (remember the set and reset are backwards on my drawing). <p>The real reason I responded was that it was pointed out to me that you would also need some sort of timer on the reset as well to account for the case where you ex...
by haklesup
Thu Aug 07, 2003 3:25 pm
Forum: General Discussion
Topic: Dakota Digital Camera $11
Replies: 5
Views: 1060

Re: Dakota Digital Camera $11

Sometimes the dumbest ideas make the most money; remember the pet rock.<p>I see it as a natural evolution of an already established market. The price is probably almost exactly the cost of such a product, so if it can be reused even one time, that constitutes a 100% profit (minus packaging and distr...
by haklesup
Wed Aug 06, 2003 6:12 pm
Forum: General Discussion
Topic: Ben Clock on Ebay!
Replies: 15
Views: 2740

Re: Ben Clock on Ebay!

Wow, If I could sell all my home brew projects for $500 bucks a pop. Ha!<p>The PCB and controller chip looks to be a good deal though. You couldn't Fab a board like that pictured for less than $150 (total for 5 pcs) and you would have to buy 5 (probably what he did). I think it would be more fun to ...
by haklesup
Wed Aug 06, 2003 5:54 pm
Forum: General Discussion
Topic: This should be a simple timer circuit
Replies: 7
Views: 1018

Re: This should be a simple timer circuit

Turn the schematic upside down and replace the ground with the battery except for RY2. It would work also if RY2 were on the other side of RY1 as well.<p>I drew it that way because most door post switches have one wire that contacts to chassis ground. To switch the hot side, you need a switch with 2...
by haklesup
Wed Aug 06, 2003 2:38 pm
Forum: General Discussion
Topic: 5 sided semi enclosures
Replies: 2
Views: 579

Re: 5 sided semi enclosures

A slope front enclosure would probably look good as a control panel. You can have the back opened up and some come with removable panels. In addition to LMB (aka LMB Heeger)also look at Bud Boxes, Serpac and Hammond enclosures. These are often stocked at many electronics retailors. I also think http...
by haklesup
Wed Aug 06, 2003 2:21 pm
Forum: General Discussion
Topic: This should be a simple timer circuit
Replies: 7
Views: 1018

Re: This should be a simple timer circuit

At the core, a flip flop would work. The circuit would be continuously powered. The door frame button would serve as the set signal and the Accessory power would serve as the reset signal. Naturally you would need some other components to scale the voltage and interface to the relay but that should ...