Clowns Hobbies Bellville

admin 2013-12-31 05:34:26
admin

Company/Business Clowns Hobbies Bellville
Website http://www.clownshobbies.co.za/
Business Type Reseller
Category/Genre Hobbies – Radio Control
Posted By
admin

Core Business Specialist hobby store
Address 1 Shop 12 Old Oak Centre
Address 2 Corner Meerlust / Suikerbossie Streets
Suburb Bellville
Town/City Cape Town
Region Western Cape
Country South Africa
Zip/Postal Code 7530
Telephone 021 910 0602
Details/Additional

Clowns Hobbies is your specialist hobby store. we are conveniently situated in Milnerton and Bellville, Cape Town, South Africa. We specialise in radio control Aircraft, Helis, boats and cars. We also stock all kinds of hobby tools and accesories, Slot Cars, Plastic Models, Wooden ships, and much more. This site does not contain our entire stock listing or prices, as we use it to showcase the latest offerings and specials.

We are one of SA’s largest importers and stockists of Model Fuel, Hobby Accesories, Electronics and Balsa wood. We pride ourselves in forming long lasting relationships with our customers through friendly, HONEST and expert service. Our Mission is to grow the RC modelling hobby in SA to levels never seen before.
Why not pop into one of our branches today, and see for yourself why Clowns Hobbies is a cut above the rest!


Clowns Hobbies Milnerton

admin 2013-12-31 05:34:26
admin

Company/Business Clowns Hobbies Milnerton
Website http://www.clownshobbies.co.za/
Business Type Reseller
Category/Genre Hobbies – Radio Control
Posted By
admin

Core Business Specialist hobby store
Address 1 Unit B39 Sanlam Business Park
Address 2 Corner Racecourse / Koeberg Roads
Suburb Milnerton
Town/City Cape Town
Region Western Cape
Country South Africa
Zip/Postal Code 7441
Telephone 021 555 1126
Details/Additional

Clowns Hobbies is your specialist hobby store. we are conveniently situated in Milnerton and Bellville, Cape Town, South Africa. We specialise in radio control Aircraft, Helis, boats and cars. We also stock all kinds of hobby tools and accesories, Slot Cars, Plastic Models, Wooden ships, and much more. This site does not contain our entire stock listing or prices, as we use it to showcase the latest offerings and specials.

We are one of SA’s largest importers and stockists of Model Fuel, Hobby Accessories, Electronics and Balsa wood. We pride ourselves in forming long lasting relationships with our customers through friendly, HONEST and expert service. Our Mission is to grow the RC modelling hobby in SA to levels never seen before.
Why not pop into one of our branches today, and see for yourself why Clowns Hobbies is a cut above the rest!


The dB or Decibel Measurement

Decibel Measurement

Decibel Measurement – back in time to the A. Bell Transmission line.

Although Decibel measurement goes back to the beginnings of time and many complain about its cumbersomeness in the audio engineering world it is one of the most widely used but not necessarily understood expressions.

Decibel Measurement
The Founder Father of the Decibel: Alexander Graham Bell – Public Domain

Seen that ‘to make your amplifier sound twice as loud you need to increase the power by tenfold’ many times in books and forums? Yes, it is true – your amplifier’s sound output may be twice the power of your neighbours but sounds the same on an intensity level. Even your potentiometer inside your amplifier to turn the volume up and down to compensate for our ridiculous logarithmic hearing properties.

Years back almost all audio equipment would be rated as having an output of x-Watts into a load of y-Ohms and hopefully measured at z-Hertz for i-minutes. This was simple to understand. The preamplifier output was x-millivolts into y-Ohms and if it was just a power amplifier it required x-millivolts into y-Ohms to get maximum power out. Nowadays everything is in dBu and dBm. Confused? Yes, this does create confusion because it means absolutely nothing to the layman but plenty to the layman. We need to go back in time to find some sort of coherence here.

Volts, Amperes, Ohms, Watts and the Decibel Measurement

When wanting to express the power supply voltage we would state that the voltage is ‘x’ Volts with reference to ground at a specific point. When fault finding we would be looking at the manufacturer supply rail voltages with reference to a specific point at a certain condition. Always use a reference point and make sure it is the correct reference point. Current seems to be simpler but is not – it is the current flowing through a specific branch of the circuit when the supply voltage is measured at ‘x’ volts with reference to a single point. When doing fault finding you need to know the values of the voltages and currents in a certain fixed condition  – i.e. the amplifier is idle, no input signal, usually input shorted to ground. If this condition is random you will not be able to determine whether the circuit is measuring accurately or not. Often the DC voltage measurement is all that is required but unfortunately the more experienced will tell you that transistors do and can show proper B-C-E or D-S-G readings but in fact have low gain. I have found this often in video circuitry. (television receivers and radar displays).

You can always calculate either resistance, voltage or current by also knowing only two of these parameters and using Ohm’s Law determine the missing:

Ohms Law Triangle

V = IxR, I=V/R, R=V/I

The Watt is a measurement of power and needs the user to know at least two parameters to determine the power value; P = I x V, P = (V^2)/R or P = I^2 x R. This power rating is known as DC Power. AC power ratings are more complex.

The Decibel Measurement

The Decibel is one tenth of a Bel (Alexander Graham Bel) – one Bel is a very large quantity. The Decibel or dB is not an easily understood ‘unit’ as can be determined by the amount of times its usage is misconstrued in forums and articles on the internet. The Decibel (dB) is logarithmic and is used to determine the ratio between units of power (e.g. preamplifier input versus preamplifier output) or units of field (voltage amplitude) where this ratio can be amplified or attenuated, indicated as +dB or -dB respectively. The formula is as follows:

dB Log

The other instance of dB usage is when determining the ratio between two fields, usually amplitude as in V R.M.S:

dB Field

What is the difference between these two? Nothing really. Power is proportional to the amplitude of the voltage over a known resistance, rather as in a.c. circuits this would be measured as an impedance and not as a resistance which we like to think of as a d.c. component (measurement) and is purely resistive meaning no inductive or capacitive components. Going back in time the original measurements were taken over one mile of cable at approximately 800Hz to show the attenuation. Beyond a certain attenuation the human voice may have sounded unintelligible or not at all. Television antennae should show their gain in dB.

This leads us to the standard formula for making fast calculations to determine voltage or power gain where we have substuted Ai and Ao for V1 and V2. Remember these two values are interchangeable to determine gain or attenuation. Note how the 20Log(A1/A2) or 20Log(V1/V2) through manipulation is now equal to 10Log(P1/P2) – remember that the dB is a unit. 2.54cm will always equal one inch. 1dB will always equal a voltage gain of 1.12 and power gain of 1.26.

db-formula

And the Reference is? The Decibal Measurement reference check.

In electronic circles we often hear of dBm. This is the logarithmic unit of power equaling 0dBm, where the output power of 1mW (one milliwatt) at 0.775V R.M.S. is dissipated into a load of 600 Ohms. This was the original transmission line equation for the dBm. However, as shown above if the known is 1mW then all other values can be calculated if the load resistance is changed.

So what is the formula?

dBm

The pitfall

Many enthusiasts throw around the equations above as if there is no tomorrow but I will get back to what was repeated time and time again in the beginning – the reference. As we have used 0.775V as a reference we forget that this applies to 1mW dissipation into a 600 Ohm line. We always need to remember this – if the voltage was 0.775V R.M.S. and the load resistance was 8 Ohms would we still be sitting at 0 dBm? Not at all. It is now 18.4 dBm. Or if the load was 0 dBm and the load was 8 Ohms the voltage is now 89.4 V R.M.S.

The pitfall here is the 0.775V reference – today we use the dBV (not lowercase ‘v’) which has no bearing on the load resistance.  Another well used term is dBu (lowercase ‘u’) which refers to unloaded at 0.775V.

The most important lesson here to note is that the 0dBm was originally intended for a power dissipation of 1mW into a load of 600 Ohms. (possibly a terminated transmission line).

Rohde & Schwarz

Download an excellent calculator (exe file) form their website here.

Online Calculator

Brilliant online calculator to see exactly how it works at Daycounter.

Next

Coming up this week: SPL

 

RC Boats – Whom is the supplier of the best boat kits in the RSA ?


admin
Forum: RC – Radio Control
Topic: RC Boats – Whom is the supplier of the best boat kits in the RSA ?
Posted by admin at December 30, 2013 at 4:51 am


Reliable Transformers

admin 2013-12-27 10:11:14
admin

Company/Business Reliable Transformers
Website http://www.reltrans.co.za
Business Type Manufacturer
Category/Genre Electrical – Transformers and Armature Winders
Posted By
admin

Core Business Manufacture/supply of all types of transformers/chokes/reactors up to 3.5MVA
Address 1 Atlas Industrial Park
Address 2 17 Lincoln Road
Suburb Benoni South
Town/City Benoni
Region Gauteng
Country South Africa
Zip/Postal Code 1501
Telephone +2711 421 2333
Details/Additional About Us
Reliable Transformers a South African transformer manufacturer has been manufacturing quality products since 1982.

For more than 30 years we have been servicing the South African and the Africa markets. Through some of our Resellers our products has been exported as far as Texas and Mexico.

From our headquarters in Benoni, 20km from Johannesburg in South Africa, we service a growing network of customers throughout Southern and Sub Saharan Africa and beyond. Continue reading “Reliable Transformers”

SMD Telecommunications

admin 2013-12-29 13:35:23
admin

Company/Business SMD Telecommunications
Website http://www.smd-marine.com/
Business Type Service
Category/Genre Electronics – Maritime
Posted By
admin

Core Business Maritime Electronics – Repairs and Sales
Address 1 53 Paarden Eiland Road
Address 2
Suburb Paarden Eiland
Town/City Cape Town
Region Western Cape
Country South Africa
Zip/Postal Code 8000
Telephone +27 021 511 0556
Details/Additional Our customer base is worldwide, be it ship or fishing boat owner, ship manager, leisure boater, manufacturer, ship’s agent, service company, SA Navy or Government Department. Close consultation and exchange of information builds a relationship of mutual trust with our clients. Our quality orientated mentality guarantees satisfied customers. Continue reading “SMD Telecommunications”

Eloff Transformers

admin 2013-12-27 10:11:14
admin

Company/Business Eloff Transformers
Website http://www.elofftransformers.co.za
Business Type Manufacturer
Category/Genre Electrical – Transformers and Armature Winders
Posted By
admin

Core Business Designers and manufacturers of AC/DC transformers
Address 1 Unit 3, Number 7,
Address 2 Dawn Road
Suburb Montague Gardens
Town/City Cape Town
Region Western Cape
Country South Africa
Zip/Postal Code 7441
Telephone +27 21 552 6800
Details/Additional

Eloff Transformers is based in Montague Gardens, just outside Cape Town, South Africa. The company has been operating for over 30 years, and as such has an extremely high level of expertise in the transformer field.

Eloff Transformers are both designers, and manufacturers of AC/DC transformers. We are always proud of our high quality of workmanship, as well as constantly improving our service and products to ensure customer satisfaction.

At present, the company is owned and managed by Rob Eloff. There is a large staff of well trained employees who are experienced and knowledgeable in the manufacture and design of AC/DC transformers.

Please feel free to browse our products page to view the latest range of transformers on offer. We have a wide variety of transformers to suit your every need! You may also contact us via the enquiries page, should you have any questions regarding our products and services.


Electronic Kits – Global Suppliers

Electronic Kits - Arduino

Electronic Kits – Warrantees and Customer Ability

Electronic Kits - Arduino
Arduino – Wiki Commons

A recent debate on electronic kits has shown either a decline in public interest or manufacturers are finding it challenging to supply kits to the general public and to have a good warranty structure in place.

It is not unknown that many electronic component suppliers do not honour warrantees, period. The main drawback to supplying kits is that the supplier does not know the customer and his or her ability. The drawback from the customer’s point of view is that often kit suppliers do not supply a schematic. Most kits have no patent or copyright so whether it has or doesn’t have a schematic is immaterial – the design is often common public knowledge.

Asian Kits

The electronic kits supplied from predominantly China and Thailand are thankfully usually high grade quality. That is in my own experience but the shopper should always do a background check and ensure that there is a proper return policy in place. This website is an official reporting ground for exactly that purpose. Post your own experiences and let the public know.

Get your facts straight

Most electronic kits are not supplied with the power supply – before embarking on a sophisticated project remember that often the power supply can cost many times more than the kit itself. Audio amplifier kits, especially the high powered units always advise the use of toroidal transformers. These transformers are very costly and depending on the area you live may not be easily obtainable except through overseas shipping where shipping charges because of the weight are exorbitant. Standard laminated transformers can suffice in most cases but are also not cheap, especially anything above 200VA. Computer power supplies are cheap – can this be used instead?  Again, not all computer supplies are equal – buy the best you can afford.

Chassis, cabinets, knobs, lights and switches all add to the cost.

Valve or Tube Audio (valves are English, tubes are USA 😎 )

Electronic Kits - Tube Depot
Courtesy Tube Depot, Memphis

Valve electronic kits are expensive. Before making any assumptions read up on the respective valves or tubes available worldwide. Mostly valves are imports from China or Russia whom still keep tooling to make vacuum tubes. They can be vastly different, both in terms of anticipated lifespan and in sonic quality. Likewise with audio transformers the quality is known to vary substantially from supplier to supplier. Valve amplifiers and electronic kits use high voltages so is not aimed at the inexperienced.

For the moderate or advanced kit builder I can recommend TubeDepot at http://tubedepot.com

Experiences

Over the last 4 months I have built three electronic kits – one was a 350W 4 Ohm audio amplifier (2 for the price of one) which was shipped from Hong Kong going under the kit name of L21 (V9). I was extremely impressed by the quality and shipping lead time but not by our local postal authorities. (lay in customs for three weeks). The second was a Velleman loudspeaker protector (K4700) and the last supply was kit from Maplin which allows bridging of their Mosfet amplifier. This was not impressive – no schematic and the component layout, on the documentation provided was very faded which appeared to duplicate part numbers. So no schematic and you don’t know what components to use. I’m not going to complain though as I am reverse engineering this product and will post my findings on these pages.

Out of the three the L20 wins hands down. Quality of board, quality of components and just, well a very cool experience.

Links to Electronic Kits

Firstly, I have not tried these companies listed so make no promises – I do have a few contacts that have built the kits from Tube Depot and make high recommendations from quality to after sales service.

ESP – although I have not tried any of Rod Elliott’s products (PCBs) I do believe based on his passion, experience and first class web site, for audio this should be your first port of call. Note that you will have to source your own components. His website is extremely informative with practical know-how as well as great technical write-ups for the beginner and engineer.

Micro-controllers

I have left out Arduino which is also our feature image as well as Raspberry Pi. Check your local suppliers. More on this later.

Comments

Please give me links to global suppliers of electronic kits where you have had good experiences. Global suppliers please send me the links to your products so I can add them to a separate listing. This does not necessarily have to be electronic kits: auto parts, kits, accessory links are also required. Please use the ‘add business’ facility as well to promote your business on this website.

 

Communica

admin 2013-12-27 10:03:29
admin

Company/Business Communica
Website http://www.communica.co.za
Business Type Reseller
Category/Genre Electronics – DIY
Posted By
admin

Core Business Electronics Distributor, Industrial and DIY
Address 1 53 Landmarks Avenue
Address 2
Suburb Samrand, Centurion
Town/City Pretoria
Region Gauteng
Country South Africa
Zip/Postal Code 0157
Telephone +27 (012) 657 3500
Details/Additional

Communica (Pty) Ltd was established in 1977, employing four people in Pretoria West. From these humble beginnings as your friendly corner hobby store the company has grown to one of Southern Africa’s largest independent distributors. Headquartered in Samrand with branches in Pretoria City and Cape Town, a sub-distributor network throughout the country and subsidiary companies in consumer and industrial sectors, Communica now employs 135 people.

EXPORT ACTIVITIES
Mainly SADC countries and some exports to Central, East and West Africa as well as Canada, Europe, UK and USA.

OPERATION
At Communica, sales are done at three levels: Retail Sales – We still maintain retail outlets where no minimum quantities apply and service hobbyists, students, technicians, design engineers etc. These are manned by a team of counter sales personnel and supported by product specialists. Telesales – This department services all small to medium OEMs, contract manufacturer and end user accounts who purchase larger volumes. Orders are entered by sales persons directly for onward processing and delivery. These departments are serviced by a total sales team of 14 at all branches. The field sales team undertake daily customer visits to all our medium and corporate OEMs and support design engineers and purchasing personnel with their requirements. This team supports customers from sampling and prototyping through to final production.


Mantech

admin 2013-12-27 10:04:40
admin

Company/Business Mantech
Website http://www.mantech.co.za
Business Type Reseller
Category/Genre Electronics – Industrial
Posted By
admin

Core Business Reseller and Wholesaler of electronic components and test equipment.
Address 1 32 Laub Street
Address 2
Suburb New Centre
Town/City Johannesburg
Region Gauteng
Country South Africa
Zip/Postal Code 2023
Telephone +2711 493 9307
Details/Additional

Mantech is an international marketer and distributor of electronic components, tools, consumables, test equipment and industrial products.

MANTECH was established in 1987 and in the year 2001, it merged with MOBICON – an Electronics group listed on the Hong Kong Stock Exchange.

Mantech is based in South Africa , operating through its headquarters in Johannesburg and a network of branches in Durban and Cape Town.

Our resources are strategically aimed at serving and fulfilling all industrial and non-industrial market demands (including avid hobbyists, researchers and educational institutions).

MANTECH only associates and deals with reputable and well established companies and brands throughout the world.

All of MANTECH’s staff are mandated to be ethical and professional at all times, while remaining conscious of all their legal, social and environmental obligations.

MANTECH’s business strategies, product and service policies are broadly based on the principles of maximum added value for all stakeholders.

Our products are guaranteed and we provide personalised technical support.

Sub-distributors and resellers are used as an extension of our sales and distribution strategies.

Our delivery resources include our own delivery fleet, national and international courier services as well as our national postal services.