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Programmable Voltage Reference Project

A pre­ci­sion pro­gram­ma­ble volt­age ref­er­ence cir­cuit capa­ble of 0.001 to 4.095 volt out­put in 1 mV steps with an accu­ra­cy of 100 uV.

Programmable Voltage Reference circuit board top
Programmable Voltage Reference cir­cuit board top com­po­nent side, Version 1.04

This project is based on a cir­cuit designed by uChip and pre­sent­ed in the Sparkfun forum. There is a Github page for the orig­i­nal design. Continue read­ing “Programmable Voltage Reference Project”

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New electronics workbench build

Replacing the old par­ti­cle­board desk­top with a new bam­boo coun­ter­top and adjustable leg workbench.

Electronics shop workbench
Moving some equip­ment onto the work­bench before shelve install

I had quick­ly run out of room for all my test equip­ment on my orig­i­nal desk­top table that I used for elec­tron­ics work. Leaving me around 1.5 sq/ft of usable area for my projects.
With the win­ning of an Ebay bid for a vin­tage Tektronix dig­i­tal oscil­lo­scope, I was out of room. Continue read­ing “New elec­tron­ics work­bench build”

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The DIY Open EVSE Project

The Open EVSE project includes hard­ware and soft­ware for charg­ing elec­tric vehi­cles and plug-in hybrids using the J1772 stan­dard.OpenEVSE4.23topA cur­rent DIY Open EVSE V4.23 com­plet­ed board

I start­ed work­ing with the Open EVSE project back in 2011 when I leased my first Nissan Leaf elec­tric car. Chris Howell had start­ed a post on the “My Nissan Leaf” forum and built a few pro­to­type boards to test. Then Lincomatic began work­ing on soft­ware and things began to real­ly pick up speed. Chris made the DIY Open EVSE open source on 27 October 2011, and the first boards start­ed ship­ping in late December.
Unfortunately there was a long wait­ing list to get the boards, so I decid­ed to make one for myself using the EagleCAD files pro­vid­ed from Chris.

Continue read­ing “The DIY Open EVSE Project”

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10K ohm reference resistor

A quick and easy project to mount a pre­ci­sion 10K ohm resis­tor for use as a ref­er­ence standard.

10KreferenceFront0110K resis­tor enclo­sure front panel

To go along with my Quad pre­ci­sion volt­age ref­er­ence I want­ed to add an accu­rate resis­tance ref­er­ence to my bench equipment.
I decid­ed on a 10K ohm pre­ci­sion resis­tor from Vishay Foil Resistors.
The resis­tor is a Z series ultra high pre­ci­sion Z‑Foil though-hole resis­tor with a TCR of ± 0.05 ppm/°C, Tolerance of ± 0.005 % (50 ppm), Load Life Stability of ± 0.005 %, and rat­ed at 0.6 Watts.

Continue read­ing “10K ohm ref­er­ence resistor”

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Voltage Reference Quad Project

Precision Reference Standard Quad front panel

After see­ing sev­er­al oth­er volt­age ref­er­ence projects online and many more assem­bled boards on Ebay, I decid­ed to put togeth­er my own ver­sion of a mul­ti-out­put mod­ule that I could use for pro­to­typ­ing ADC, and oth­er projects.
I need­ed at least a 2.048 volt and a 4.096 volt pre­ci­sion ref­er­ence. An extreme­ly high accu­ra­cy 5.000 volt ref­er­ence was also on my list. I already had an enclo­sure on hand that I want­ed to use, but in my ear­ly mock ups the three out­puts on the front pan­el just did­n’t look right. So for good mea­sure a 2.500 volt ref­er­ence was added to the project.

The 4.096 volt and low­er ref­er­ence IC’s only required a sta­ble 5 volt sup­ply, but the 5.000 volt ref­er­ence IC required a min­i­mum of 9 volts and prefer­ably 10 volts for max­i­mum sta­bil­i­ty. So a sep­a­rate add-on board was designed to sup­ply 9 or 10 volts along with a warm-up timer and bat­tery low volt­age alert.

Continue read­ing “Voltage Reference Quad Project”
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Milliohm Meter

MilliOhm Meter Display 0.025ohmThe Milliohm Meter Project

I built this mil­liohm meter sev­er­al months ago which is based on a project by Scullcom Hobby Electronics and pre­sent­ed on YouTube.

Louis at Scullcom Hobby Electronics has a new video updat­ing the mil­liohm meter, and fea­tures the board I pro­duced in this post.
NEW Link to updat­ed video on YouTube
NEW Version 1.5 board avail­able at OSH Park requires addi­tion­al 0.01 uF ceram­ic capac­i­tor, 2 pin head­er, and 250 mA PTC fuse.
NEW Updated project post with Milliohm Meter ver­sion 1.5 board.

It uses a 4 wire kelvin mea­sure­ment sys­tem that sup­plies a pre­cise 100 mA cur­rent to the device under test using one pair of leads, and then mea­sures the volt­age drop across the device under test using a sec­ond pair of leads.
As designed it can be used to mea­sure low resis­tances of under 2 ohms (Ω).   Some of the design changes I made to fit my needs were:

  • Change the num­ber of resis­tors need­ed in the cur­rent source circuit
  • Use high­er pre­ci­sion resis­tors with a low tem­per­a­ture coefficient
  • Add sep­a­ra­tion and shield­ing between input, out­put, and sup­ply circuits
  • Use low­er ESR and high­er val­ue capac­i­tors for the MAX680 pow­er supply
  • Add addi­tion­al decou­pling capac­i­tors on the INA106, and MAX680 IC’s
  • Change the volt­age reg­u­la­tor from a TO220 pack­age to a SOT-223 package

Continue read­ing “Milliohm Meter”

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Millivolt Meter


The Millivolt Meter Project

This is a DIY mil­li­volt meter that was orig­i­nal­ly designed by
Scullcom Hobby Electronics and pre­sent­ed on Youtube.
Definitely take the time to watch the videos (4 parts) as they are very well done and pre­sent­ed in a way that’s easy to fol­low and learn from.

I was in need of a meter that I could ded­i­cate to low volt­age pre­ci­sion read­ings, and could be done for a rea­son­able cost. So this project seemed like a per­fect fit. As usu­al after view­ing the video I saw many areas that the meter could be mod­i­fied and improved for my spe­cif­ic use, and quick­ly began design­ing my own ver­sion of it using Eagle CAD V7.5.

Continue read­ing “Millivolt Meter”
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