{"id":389,"date":"2017-01-08T16:47:13","date_gmt":"2017-01-08T16:47:13","guid":{"rendered":"http:\/\/bassett.me\/mike\/blog\/wordpress\/?p=389"},"modified":"2020-06-17T16:57:24","modified_gmt":"2020-06-17T15:57:24","slug":"analogue-function-generator","status":"publish","type":"post","link":"https:\/\/bassett.me\/mike\/blog\/wordpress\/electronics\/analogue-function-generator\/","title":{"rendered":"Analogue Function Generator"},"content":{"rendered":"

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Every electronics lab needs a function generator! <\/span>\u00a0<\/span>The one describe here, when fully built, produces sine, square and triangle waves at a range of frequencies from about 0.25Hz up to about 160kHz. A symmetry control is available which will vary the slope on the triangle wave and the ratio of the square wave; it also does strange, but predictable, things to the sine output. If the full unit is built, then the output will be up to about plus or minus 6V and capable of supplying about 200mA; though the continuous power is fairly small so it cannot supply the full voltage and current simultaneously for very long but you can apply a heatsink to extend this capability. <\/span>\u00a0<\/span>The OPA551 amplifier used as the output does however have thermal and current limits and a signal output for when they are exceeded.<\/span>\u00a0 <\/span>Nothing is calibrated but there is space on the control panel to put stickers for your favourite settings.<\/span><\/p>\n

Most of the parts are available from CPC Farnell and the prices given are approximate as of 2016.<\/span>\u00a0 <\/span>Some of the lower cost parts are only available in small bulk but the excess components are generally useful for your bits\u2019 box.<\/span>\u00a0 <\/span>The nuts, bolts and washers I got off amazon from Connex, part numbers DP8500055 and DP8500056.<\/span>\u00a0 <\/span>One is a kit of nuts and bolts and the other of washers.<\/span>\u00a0 <\/span>These kits are both very useful and a worthwhile addition to your bit\u2019s box.<\/span>\u00a0 <\/span>They cost about \u00a35 each with p&p about the same.<\/span><\/p>\n

The unit is built on a custom printed circuit board which you will need to have made up.<\/span>\u00a0 <\/span>There are several manufacturers providing a range of services.<\/span>\u00a0 <\/span>Some will provide 1 board quickly and some 10 boards slowly but all cost roughly \u00a330.<\/span>\u00a0 <\/span>So if you want 10 boards and don\u2019t mind waiting about 4 weeks you buy your boards from China \u2013 I use iTead.<\/span>\u00a0 <\/span>If you want one board quickly you get them from Europe \u2013 sometimes within a day or two.<\/span>\u00a0 <\/span>Whichever service you use you will almost always require the Gerber files.<\/span>\u00a0 <\/span>These are a set of several text files which describe in detail how your board will be created, layer by layer.<\/span>\u00a0 <\/span>I used Eagle to create my design and having tried several other circuit design programs this is my preferred one.<\/span>\u00a0 <\/span>Possibly due to reading Simon Monks excellent book on the subject.<\/span>\u00a0 <\/span>I hate re-inventing the wheel and Simons book describes the whole process exceptionally well.<\/span><\/p>\n

There are 2 templates included which need to be printed to scale so that the control panel width is 165mm and the height is 210mm and the holes in the IEC C14 connector are 40mm apart.<\/span>\u00a0 <\/span>If printed to a scale of 100% this should be right.<\/span>\u00a0 <\/span>Do not be tempted to print once and photocopy the second unless the photocopy is a better size in which case use 2 photocopies.<\/span>\u00a0 <\/span>The front panel template is used twice and if both templates are not exactly the same size it won\u2019t work correctly.<\/span>\u00a0 <\/span>Photocopiers rarely produce an exact scale copy.<\/span><\/p>\n

Tools you will need<\/span><\/h2>\n

You may have several of these from previous projects.<\/span><\/p>\n