| Electronics > Projects, Designs, and Technical Stuff |
| Home Brew Analog Computer System |
| << < (21/66) > >> |
| GK:
It would be really difficult to estimate the total time spent; Hundreds of hours. Note that those integrator boards pictured constitute probably ~5% of the total circuitry. I reasoned that the cost in monetary terms is justified alone by the educational benefit conferred by having a full blown differential analyser on which to apply problems in physical systems modelling and differential calculus. If you can pardon my immodesty, I think this is going to be quite an impressive (two relay-rack) machine when finished. An eventual hyperlink to a full expository technical write up on my web domain probably won’t hurt my resume either. |
| GK:
--- Quote from: SeanB on November 28, 2012, 04:03:00 pm ---I used to have a box of mechanical sine/cosine resolvers and hundreds of other styles of synchros and resolvers, they were parts of anb autopilot. We were cannibalising them for spares to fix moving map displays and other synchro indicators --- End quote --- Hey, you wouldn't happen to have by chance a few sine-cosine potentiometers laying around, would you? I've got a prototype matrix computational circuit on the go which transforms the Cartesian coordinates (X,Y,Z) of 3-dimensional objects and graphs into 2-dimensional polar coordinates (X,Y) for isometric projection on a 2-dimensional display. However at the moment the angles of rotation of the isometric projection around the x and y axis' are fixed and in order to make them independently and continuously variable I require a pair of sine-cosine law potentiometers. Such things still appear to be available new: http://www.precisionsales.com/potentiometers/singleturn/sinecosine.htm .........however I'm afraid to even bother asking what they cost. One possible alternative is to fake the dual sine-cosine law with digital pots driven by a rotary encoder via a uC programmed with appropriate look up tables (or just solving each increment) but even with lots of "linear" bits to work with the steps still get quite chunky at the extremes where the rate of change is high and many "counts" are skipped. A pair of "old school" pots are still the preferred option. These kind of pots were used extensively back in the day for radar displays (2-D projection of 3-D) and early medical imaging equipment. |
| SeanB:
Sorry, they stayed when I left. |
| GK:
Poo. It looks like I'm stuck with digital pots and a uC. Looking at the datasheets a little closer those sine-cosine pots from Precision Sales aren't the right type anyhow. I reguire a pair of the quad wiper radar display types which operated over 90 degrees of shaft rotation. A pair of A5204's and a PIC16F874 with sin/cos look-up tables it is for now. |
| chickenHeadKnob:
I can't tell what kind of latency you need from your synthetic pots, but you might find the classic CORDIC algorithm a useful speed/accuracy/table size trade-off. CORDIC by its very nature simultaneously computes SIN and COS for a given theta and requires a much smaller table once the number of bits of resolution desired goes up. |
| Navigation |
| Message Index |
| Next page |
| Previous page |