A question for you PI design experts

[Charles (Upstate NY)]

How difficult would it be for an electronics novice to build a PI and understand how it works? I have been thinking of jumping into this as a fun project for a few years now but I'm a computer software guru not an electronics guru.

I can build coils and managed to rewire my mill for 220vac without melting my service panel so I'm not completely void of electrical skills. Still I'm not sure I want to invest the time and engery if my prospects for success are low.

Are there any computer software applications out there today which would make this easier?

Thanks in advance for your feedback.

[pml]

I know that I'm probably the last you'd want to hear from, , but IMHO don't ever limit yourself. I am self-taught at everything.

As for understanding how it works, you could use something like Spice. I think Spice is probably the most widely used circuit simulation software. PSpice is also nice. Unfortunetly they cost money. I like using a free online applet Circuit Simulation for doing quick stuff ->

http://www.falstad.com/circuit/

What's nice is that you can see live simulation while you tweak and/or add parts. Although it's not nearly as powerful.

Filter Solutions 2006 is great for filters:

http://www.filter-solutions.com/


Paul

[bbsailor]

Charles,

Go for it! There are folks on this forum that can walk you through assembling your Hammerhead.

You will need a few tools.

Small tip soldering iron 15 to 20 watts.
Digital Multimeter
Oscilloscope (optional but helpful)
Magnifying glass to insepect soldered connections
Power Supply (optional but helpful) or a 12 volt recharagable battery.

For starters, here are some helpful tips.

1. Obtain the circuit board from Carl. This is much easier than making one.
2. Decide which version you want to build (VCO audio out or non-VCO)
3. Make a list of all the parts for the version you pan to build. Note: you must purchase parts that fit the mechanical size and spacing of the component holes. Study posted photos of completed HammerHead circuit boards.
4. Use .25 watt 1% metal film resistors. Purchase a variety of .5 watt resistor values between 680 ohms and 1000 ohms for R11. Install R11 last after the circuit is operational and tuned.
5. Build the coil with Teflon Insulated wire
6. Order the parts on-line. Review past posts for some recommended parts substitutions.
7. Check out your local Radio Shack for some less critical parts
8. Take your time and assemble it in stages as suggested in Carl's instructions.
9. Take measurements as you assemble in stages and annotate the schematic. Look at signals on the scope the see how the circuit is working. This make debugging easier later if needed.
10. Decide which adjustments you want external (use pots) or internal (use trimmers).
11. Have fun!

Keep us posted about your progress.

bbsailor

[bbsailor]

Charles,

This question took a little longer to answer.

Are there any computer software applications out there today which would make this easier?

Yes.

Electronics Workbench allows you to construct the circuit on the computer and then simulate the circuit operation with different component values and see the operation on a virtual Oscilloscope. Hammerhead IC5, the main PI timer, is a good circuit to start building in simulation and then physically. This will help you appreciate the relationship between pulse frequency and pulse width as it relates to the operation of the Hammerhead PI circuits which are described in detail in Carl's instructions.

Go to the link below (good variety of kits available) to purchase premade kits (LM555 IC kit) that you can wire up and then inspect with a scope. http://www.vakits.com/index.php?cPat...989fcab0c28a87

Check ebay for some 20 Mhz or higher 2 channel scopes that can be had for about $100.00. Get 2 sets of 10 to 1 probes also.

This will start you on a life-long journey to understanding squiggle lines and cryptic symbols called schematics that have meaning to those who can translate their abstract meaning to build useful devices that work. Come to think of it, this is not too different from understanding software.

bbsailor

[Charles (Upstate NY)]

I know that I'm probably the last you'd want to hear from, , but IMHO don't ever limit yourself. I am self-taught at everything. Paul

Paul give me a second here, I'm still a little dizzy from blacking out and falling out of my chair!

Your reponse was a textbook example of why we like Geotech, a supportive response with useful information. Please continue on this path and yesterday is old news already.

I did a quick google, Spice seems very similar to the CAD/CAM racket uh-er I mean packages. Prices range from $300-$8,000. Most are inexpensive compared to what I dropped on my CAD/CAM software so that much is encouraging.

I already have some equipment as well, not sure how applicable it would be to building a PI. I have a analog scope, a digital Picoscope, a function generator, BK LCR meter, BK 50k count Multi-meter, all purchased new in the last 3-4 years.

There are few DIY projects I fear, plumbing and autobody work come to mind. Hang around here long enough and you will see some examples (not all good) of my adventures. I tend to want to bash small parts I fumble and drop with a hammer so I'm not sure I have the temperment for building a curcuit board. Of course there's always NCDave's story of the exploding PI, I mean do you guys wear Kevlar shop aprins?

Anyway thank you for the information and good to see a great post from you.

Charles

[pml]

I forgot to mention there's also a free downloadable version of Pspice with some limitations.



http://www.electronics-lab.com/downloads/schematic/013/





Limits
The following limits apply to the Student Version of the products:

PSpice A/D
Circuit simulation is limited to circuits with up to:

• 64 nodes
• 10 transistors
• 65 digital primitive devices
• 10 transmission lines in total (ideal or non-ideal)
• 4 pairwise coupled transmission lines.

Additional limits:

·The sample library includes 39 analog and 134 digital parts.

·Device characterization in the PSpice Model Editor is limited to diodes.

·Stimulus generation in the PSpice Stimulus Editor is limited to sine waves (analog) and clocks (digital).

·Circuit optimization with the PSpice Optimizer is limited to one goal, one parameter, and one constraint.

·You can not create CSDF format data files.

·You can only display simulation data from simulations performed with the Student Version of the simulator.

Schematics

·You can place a maximum of 50 parts on a schematic design.

·You can only draw on size A sheets.

Capture

·The PSpice libraries are the only ones included. The standard Capture libraries are not included.

·Import facilities, netlisters, and accessories that are not relevant to PSpice are not included.

·You can not save a design that contains more than 60 parts. (You can view or create larger designs, but you can not save them.)

·You can not save a library that contains more than 15 parts.

[Charles (Upstate NY)]

Charles,
Go for it! There are folks on this forum that can walk you through assembling your Hammerhead.
bbsailor

Cool I already have the required test equipment. Building a Hammerhead sounds like an excellent way to get started and gain an understanding which is mostly what I'm looking for here. I mean lets be realistic it is doubtful I would be able to approach an Eric Foster or Dave Emery PI machine in terms of performance and when I hunt I typicaly want the best machine but I may one day be able to modifiy such a machine to add features I want. I think that is a realistic goal.

My Explorer for example is a fantastic machine but there are many features I would design differently. I'd definately change the tone ID around. I'd have hot buttons for certain features versus navigating a combersome menu. Refinements not core design changes.

Charles

[Charles (Upstate NY)]

Come to think of it, this is not too different from understanding software.
bbsailor

Now that is interesting. I have been designing computer software since 1982. Hmmm a PI with a color LCD, gps, and bluetooth wireless logging to my pocket PC?

If I can just get NCDave to add bluetooth to the Pulse Devil...

Charles

[pml]

I'm glad you posted this thread Charles. Out of curiosity I did a search on free circuit simulators and came across SPICE OPUS. It looks nice and it's free. Was wondering if anyone knows much about it.

http://fides.fe.uni-lj.si/spice/


Paul

[Carl-NC]

I hate to plug the competition, but Linear Technology also has a free Spice program. The schematic capture really sucks, but it is all nicely integrated and easy to use. The sim engine is probably Berkeley 3C, so there should be no limitations.

Charles, if you can wire up the CNC for your mill, you can build a PI. Also, plumbing is easier than building a ckt, auto body work a little harder. IMO.

[Charles (Upstate NY)]

Also, plumbing is easier than building a ckt, auto body work a little harder. IMO.

Carl I have a plumbing jinx. Rusted together pipes, rounded off nuts, maybe thats normal but I'm talking bizzare. Last year I went upstairs to use the toilet. (NCDave that's a loo). I went back to the shop in the basement and heard water running. Well that toilet fills slow as a snail so I didn't think much of it. About a half hour later I notice the water is still running. I often have to jiggle the handle so no biggie. About another half hour goes by and I finally go back up there. I go into the bathroom and...the toilet is fine. Hmmm I go back out into the hall and hear the water running louder.

I head down to the kitchen thinking the cats turned the faucet on but nope. Hmmm I go back upstairs to the master bathroom which I rarely use (its a half bath) open the door and theres freaking 2-3 inches of water on the floor. The supply line for the toilet had blown off. It was not broken, just disconnected. The connection was fine for 50 years then I buy the place and well tell me thats not weird. The water had run through the floor into the garage, and was clear down the driveway and running down the street.

Since this is only one of many such stories it suffices to say a year later I still have to jiggle the handle on the other toilet.

[J_Player]

Hi Charles (Upstate NY),
It sounds like you have most of what you need to build a Hammerhead PI except maybe an oscilloscope. If you don't have a temperament for working with circuit boards, here are some things that can help save a lot of grief:

1. Get a small benchtop vice that has a swivel designed to hold a circuit board. Do your soldering with the board in this vice. You can also get benchtop holders with alligator clips that will hold wires and other parts in place if you think that is helpful.

2. put a large magnifying glass in front of the board while you are soldering. This makes things a lot easier. There are bench-mount magnifying glasses with lights attached that work excellent.

3. Use a low-wattage soldering iron as suggested. The kind with a pointy tip works good for circuit board work. Keep a damp rag nearby to clean the crusty stuff off the tip before making a solder joint. When soldering a joint, the tip of the iron should have a little shiny solder on it.

4. Learn how to solder like a pro. This means dab a little flux on each joint before you solder it, even if you are using flux-core solder. Then when you are done soldering, clean off the joint with alcohol until it is squeaky clean. Use only enough heat and solder to get the job done. The finished joint should not have any big globs of solder hanging to the side, and no voids, just a clean shiny fillet of solder at the joint. Make sure there are no solder bridges shorting the joint to an adjacent conductor on the board, and there are no "little droplets" of solder stuck where they don't belong.

Note: Don't use acid core solder or acid flux designed for plumbing. The acid flux will corrode your circuit board. Use solder and flux designed for electrical work.

If you do those 4 steps, you will save yourself 90% of the grief that most people run into in their first soldering projects.

[Reg]

Hi Carl,

Can you provide a link to the spice program? I couldn't find anything except one that works on switching power supplies.

Thanks,

Reg

[Qiaozhi]

SPICE Simulator

Hi Charles,

Try this (it's free) -> http://www.aimspice.com/about.html

By the way, for those that do not already know, SPICE stands for Simulation Program with Integrated Circuit Emphasis.

If you're a programmer and understand some basic electronics, you shouldn't have too much trouble with the nuances of the SPICE world.

Personally I've not used AIMSPICE, but I'm a long time user of several other SPICE packages. Any problems - just ask.

In case you want to explore some alternatives to AIMSPICE -> http://www.repairfaq.org/ELE/F_Free_Spice2.html

Have fun!

[pml]

Carl,

The Linear Tech Spice sounds great. I love their high performance parts op-amps and ADC. Are you talking about LTSpice/SwitcherCAD III?

http://www.linear.com/designtools/so...gistration.jsp

http://www.linear.com/company/software.jsp

Thanks,
Paul