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I ~ 1/"•• ~ . "~-:'. Electronics workbench for home or laboratory Are you presently wprking under difficult conditions on an unsatisfactory workbench? You don't even have a workbench? Then cast your eyes over this design and see if it would suit your requirements. By LEO SIMPSON This workbench design was built for the SILICON CHIP workshop a number of years ago and it has generally proved to be practical and effective. We had four of the benches built in fact, and if we were having them built again we would only make slight changes. These changes have been incorporated into the dimensional draw82 SILICON CHIP ing (Fig.1) featured with this article. Our requirement was for a workbench that had plenty of space, was reasonably strong without being too heavy and which could be disassembled so that if and when we moved premises, which we did, the job would not be too onerous. A workbench for electronics assem- bly or service work should not be something slapped together after five minutes' thought. Nor should it follow the lines of a workbench intended for a carpenter or fitter and turner. Our first requirement was that the bench should not be too high - just a little higher than standard desk height would be right. After all, most electronics assembly or service work is done ·sitting down, not standing. Nor should the person concerned be perched on a stool - a comfortable office chair should be used. Overall dimensions The workbench needs to be large but not so large that you cannot reach the furthest corners without stretch- r 780 L ◄ Fig.1: build your workbench to the dimensions shown in this diagram. The bench top & shelving is made from particle board, while the sub-frame & side braces are made from DAR pine or Oregon. Do not use material thinner than that specified, otherwise the bench will not be strong enough. f --LEGS OAR 50x50 FINISHED BENCH TOP 18mm PARTICLE BOARD SHELF AND SHELF SUPPORTS 15mm PARTICLE BOARD DIMENSIONS IN MILLIMETRES Pictured at left is one of four identical workbenches which were designed and made for the SILICON CHIP workshop several years ago. The design has proved quite practical but sadly, they are never quite as tidy as presented here. The legs and side braces are made from 50 x 50mm DAR timber, while the rear cross brace is made from 36 x 36mm DAR timber. This should be glued and screwed together to produce a light, strong and rigid frame. Benchtop ing too much. That is one benefit of the L-shaped extension which can be attached at the right or lefthand end. We originally intended the extension table to be used for computers but it has not worked out that way. They are not quite deep enough to be convenient for most computers and certainly not' if a big monitor is to be used. However, the extension does make a very convenient extra work space, for spreading out diagrams , data books or whatever. Hence, the overall dimensions of the workbench are 1800mm wide by 900mm deep and 780mm high; ie, the same as a standard office desk except for a small increase in height. The extension measures 900 x 640mm. The top section is 305mm high and has a shelf 375mm deep. The workbench shown in the photo has a shelf only 305mm deep but that has proved to a little shallow for equipment such as oscilloscopes. The frame of the workbench is made from 75 x 50mm DAR (dressed all round) pine or Oregon (Douglas Fir) . The top is made from 15mm thick particle board. This is fitted with locating blocks on the underside so that it merely drops into place on the frame. The particleboard is covered with flooring vinyl which makes a very comfortable working surface. It does have two drawbacks though. First, if you drop hot solder onto it, it partly melts its way into the surface, making it very hard to remove. Second, the vinyl we used has a slightly dimpled surface which is not good for writing on. If we were making the workbenches a second time, we would specify a vinyl with a smooth surface. The problem of hot solder can be partly overcome by putting down a suitable piece of felt over your immediate working area. To protect the edges of the vinyl, an 18mm timber moulding is fitted all round. This should be nailed and glued into place. Sitting on the top of the bench is the shelf assembly which is made from 16mm thick particle board finished on all surfaces with white Melamine. The shelf assembly is closed in at the sides and back. This stops things roll- ing off the bench. On our prototypes, the shelf assembly was made from standard 300mm wide shelving but as noted above, the top shelf surface really needs to be around 375mm wide to accommo date equipment like oscilloscopes. Any unfinishe d edges of the Melamine surfaced particle board can be finished with iron-on Melamine veneer. The whole assembly is screwed together and to the benchtop with particle board screws. Do not use selftappers. They do not hold as well as twin-start coarse thread screws which are made especially for particleboard. The countersunk screwheads can then be concealed w ith white plastic covers which fit into the recess of the screw h ead. L-shaped extension The frame and legs of the extension section can be permanently secured to its top section. It is then bolted to the main bench, at either the right or lefthand side, depending on your preference. Electricity Many workbenches we have seen over the years have had unsatisfactory mains power outlets. It is a mistake to put them right at the back of the bench where you will have to keep reaching for them. Nor do you want the power points at the front edge of the bench where the power cords will constantly be in the way. JULY1992 83 Protect your valuable issues Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a distinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. This photo shows a closeup of the Kambrook KDl 7 4-outlet power point used on both sides of the benches. These power points can be purchased from K-Mart for about $25 each. * High quality * Hold up to 14 issues * 80mm internal width * SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price : $A 11.95 plus $3 p&p each (NZ $6 p&p) . Send your order to : Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your cred it card number. Use this handy form l ----------Enclosed is my cheq ue/money order for $._ _ _ or please debit my O Bankcard O Visa O Mastercard Card No: Card Expiry Date __/ __ Signature _ _ __ _ _ _ _ __ Name _ _ _ _ __ __ _ __ Address_ _ _ __ _ __ __ I I I I I I II II I I I . ___________ . _ _ _ _ _ _ _ P/code_ __ 84 SILICON CHIP Putting the power points at either side of the bench is a good compromise. We used a 4-outlet power point at each side of the bench. These are made by a number of manufacturers but in our view the one made by Kambrook, model KDl 7, is the best value for money. It has shuttered outlets and double pole switches and is presently available from K-Mart stores at around $25. The mains wiring to the two GPOs (ie, power points) should be run in 10-amp rated solid core double sheathed cable, specified as "1/1.13mm twin and earth". You will need about 3.6 metres of this cable. This is run in 16mm square plastic conduit with adhesive backing and a snap-on plastic top cover. Although the conduit does come with an adhesive backing (just peel off the protective cover and stick the conduit on) we also used screws, just to make sure. You will have to notch out the shelf supporting section(s) to accommodate the conduit. The square conduit is available from electrical wholesalers. To get the power to the bench, you will need a 10-amp rated flexible power cord with moulded 3-pin plug. The cord should be at least 2.5 metres long. The cheapest way to get this is to buy a ready made 3 or 5-metre long extension lead and cut off what you don't need. The cord is anchored with a cord clamp to the shelf assembly before passing through a 10mm hole in the particle board immediately behind one of the power points. It is then anchored again with a cord clamp and terminated to the back of the power point. Other refinements Having presented this design, readers will no doubt come up with their own refinements. For example, you could add a foot rest to run between the two side braces. If you do this, make sure you use adequate strength timber such as 100 x 36mm DAR, otherwise you may snap it if you apply too much weight. And if you do add the footrest , don't be tempted to omit the rear cross brace. If you do build a workbench to this description, it will cost you several hundred dollars for material alone but it will be money well spent in providing a practical and effective work space. And then don't forget to buy a reasonable office chair to go with it. After all, you may spend quite a lot of time sitting in it. We purchased gas-lift office chairs but with one modification. We had the central column extended by 10cm to give a little extra height. Most imported office gas lift chairs are sourced from Italy or the far east and they don't adjust quite high enough for the average Australian male. SC