Monday, January 21, 2019

Measureall Workbench Test Instrument

This was a Student Project, it is a very basic instruments that could do most of the tasks on a test bench.

The cabinet used, was available as a part of a Hi-Fi DIY System, The Range and Mode switches were Modular Stackable Interlocked MultiPole Switches. The rest of the Interface were wirewound pots, jacks, sockets and plugs. The front panel was Engraved Acrylic.

I wanted it to look well engineered, at least on the outside. It was a total analog instrument except for the digital indication of ICL7107. Thanks to 'Intersil Hot Ideas' Applications Book.

MeasureAll Benchtop Instrument
The above belong to an instrument Measureall shown

Friday, January 18, 2019

Bakatronics - DIY Kits and Model Railroads

Bakatronics LLC designs and manufactures innovative electronic circuits for model railroads.  For the last decade Baka has been creating new ways to make your model railroads "come alive". 

Bakatronics - DIY Kits and Model Railroads

The Kits include the Lighthouse Flasher, Emergency Lights, Airport Beacon, Campfire and Super Welder Flash kits All are based on advance micro controller technology and will enhance any railroad.

Bakatronics - DIY Kits and Model Railroads

FK945 Digital Temperature Controller kit

This circuit can be used to control when an appliance or device turns on and off by temperature. 3 Digit Read Out and easy to set buttons.

Thursday, January 17, 2019

RS Components - Equipment Tools Parts

RS Components is the UKs largest Industrial Products Catalogue and Data Library on-line. Offering secure on-line ordering with same day despatch for Books, Cables & Connectors, Consumables, Electrical, Electronic, Health & Safety, IT, Mechanical , Office Equipment, Power Supplies, ecomm and Measurement, and Tools

RS Components - Equipment Tools Parts

RS Components - Equipment Tools Parts

RS Components is the UK, European and Asia Pacific trading brand of Electrocomponents plc. The company supplies electronic components, electrical, automation and control, and test and measurement equipment, and engineering tools and consumables through the internet, catalogues and at trade counters

RS Components was founded by J.H. Waring and P.M. Sebestyen in 1937 in London under the name Radiospares supplying radio repair shops with spare parts. When televisions became popular, television parts were added to Radiospares' product list.

Sunday, December 23, 2018

Experiments with the LM2575

The standard buck regulator circuit delivers a +5V output. This is a rather straightforward circuit and will operate with a wide spread of component values. Optimal values should be selected however to get minimal ripple, minimal noise to the power source, maximum efficiency etc. Note that the quiesent current is about 10 to 14mA.

Here is a nice way of using this regulator, Experiments with the LM2575 this can be used for CMOS opamps as you have a -5V too. That means a portable instrument may find this design useful.

The TI Datasheet Layout Guidelines

LM2575 Switching Regulator

LM2575 - Step-Down Adjustable Voltage Switching Regulator with Output Enable

The Spirit of Hacking and Fixing, Giving back Life to Old Instruments.

Fluke 8050A LCD display replaced with LED seven-segment

"Recently I was able to cheaply buy a second hand Fluke 8050A made in the early eighties. It is a nice 4.5 desktop digit meter, but a typical problem seems to be that the LCD wears out and goes black. Replacement LCD displays are hard to find, not cheap and probably lead to similar problems in due time."

Friday, December 07, 2018

LM317 based Regulated Power Supply

This is a Regulated Power Supply based on the LM317 IC. It will need a Boost Power Transistor and heatsink for higher currents. It is a versatile building block for stable instrumentation supplies. Consumer Electronic gadgets can use a SMPS chip. In case you wish to use a SMPS for a Precision Instrumentation Block, then take extreme care on Shielding and EMI-RFI.

LM317 based Regulated Power Supply

This is a General Purpose Chip, Series Regulation. It can be varied or trimmed. There is an Internal temperature compensated reference. The minimum trim value is around 1.2. In case you want a Low value voltage like 0.5 with a good current, then use a good negative supply to offset the 1.2 V.

See more at my Power Supplies Section.

The transformer can be s Split Bobbin with Pri-Sec copper shield foil.  This can be earthed along with the metal enclosure. C4 sends any hi-freq components to earth.  It is better if you do not earth the ground but use such capacitors. A Supply should simulate a a battery with both ends floating wrt Earth. A option to eartth the ground is fine. This also helps the user to configure his own dual supplies.

Q1 and R5 form a Short Circuit OR current fold back OR constant current mechanism. TP1 can be used to vary the output voltage.  Better use something like a Bourns 10T trimpot. An open preset may introduce a noise due to dust and vibration. I don’t remember why i added a zener DZ1, a diode may suffice.

delabs Schematics