Modifications for Jasic 200A TIG welder and pedal

In about 2009 I purchased a Uni-mig Jasic 200A TIG welder (though these are sold under many brands).

The welder came with unusual 2 and 5 pin connectors for the torch trigger switch and an optional pedal. The optional pedal was quoted at around $500, probably partly as the seller had locked the market up with the unusual connectors.

There is no standardisation of these connectors, but the pedal internals are pretty common. A quite common configuration is a 2 pin Foster (microphone) connector for the trigger switch and 3 pin Foster (microphone) connector for the current pot.

A further usability issue is that the pedal varies current from 5 to 200A, it is not possible to set the maximum current when the pedal is fully depressed.

So, a decision was made to:

  • buy a ‘standard’ pedal for about $50 on eBay;
  • refit the connectors on the welder;
  • add a ‘maximum current pot’ to the pedal.

Connector refit

Above is the wiring of the back of the new pedal connectors.

Above is a view of the new connector panel in place, the 2 pin plug on the left is the TIG torch. Continue reading Modifications for Jasic 200A TIG welder and pedal

BLHeli 14.8 damped light and active freewheeling

Aficionados of BLHeli call out the benefits of “damped light” and “active freewheeling”, terms coined by BLHeli’s author.

Since these are terms invented by BLHeli, so you might wonder whether they are truly innovative or just marketing hype for existing techniques.

Lets go to the BLHeli manual for an explanation.

Pwm damped light mode adds loss to the motor for faster retardation. Damped light mode always uses high pwm frequency. In damped light mode, two motor terminals are shorted when pwm is off

Taking the last statement first, in fact, what happens that as that during the OFF phase of the PWM drive, the high side FETs at both ends of the winding are turned ON. One FET is on for the whole phase, and the other one switches on a short time after its corresponding low side FET turns off. The short time is to allow the low side FET to cease conducting, otherwise both high and low side FETs would conduct at the same time, a current from battery +ve to -ve via the two FETs. There is a corresponding pause at the end of the PWM phase. The time delays allowed depend on the driver circuitry and FET performance, they are specified in the firmware  for a specific and don’t necessarily apply to a pin compatible ESC.

This technique is known in the wider community as COMPLEMENTARY PWM, a very standard technique. Continue reading BLHeli 14.8 damped light and active freewheeling

Fan controlled by humidity sensor – pre implementation data gathering

This article documents measurements of temperature and relative humidity (RH) over 10 days prior to implementing the fan solution to provide a baseline for designing the Fan controlled by humidity sensor.

A RC-4HC datalogger was used to collect temperature and RH measurements over 10 days which included a range of late winter weather, some rain, some fine clear days. The logger was located at 1.5m above floor level in the shed in a relatively clear spot in the middle of the area..

Screenshot - 22_08_16 , 15_53_17

Above is a chart of temperature and RH. The daily RH peaks are typically between 08:00 and 09:30, and pretty much coincide with the minimum observed temperature. There is clearly a lag from outside temperature which would tend to be minimum a few hours earlier, and a lower minimum (there were plenty of frosty days in the sample set). Continue reading Fan controlled by humidity sensor – pre implementation data gathering

Time to get some experience with 32bit microcontrollers – some progress

At Time to get some experience with 32bit microcontrollers I wrote that after almost 50 years working with 8bit microcomputers and microcontrollers, I thought it about time to get my hands dirty on some 32bit microcontrollers.

This article reports some work in the STM stream.

I abondoned the ST Discovery board in favour of a low cost basic ST32F103 development board costing about $4 on eBay. The chip is a 32bit microcontroller clocked at 72MHz.

As a learning vehicle, I decided to implement the functionality contained in Arduino thermistor thermometer – a tutorial.

The development environment is Eclipse with the GNU ARM toolchain, a debugger probe, the basic development board, and a 1602 LCD display with I2C backpack and an inexpensive CP2102 USB RS232-TTL interface.

ST32F103-d01

Above is the working trial. The GDB debugger allows On Chip Debugging (OCD).
Continue reading Time to get some experience with 32bit microcontrollers – some progress

Fan controlled by humidity sensor – design technique

This article gives an outline of the process used in designing the Fan controlled by humidity sensor to use my Generic heating / cooling controller design (hcctl).

Arduino thermistor thermometer – a tutorial gave a method for designing a thermometer based on a formula predicting the behaviour of the sensor. This article explains a different approach where that is not possible.

HDS10-02

Above is a characteristic from the manufacturer’s data.

The curves to no lend themselves to simple curve fits, so a cubic spine interpolation will be made based on key points from the curve.

Four our purposes, the mean curve (green) is sufficient for design.

Screenshot - 24_07_16 , 08_16_07

 

Above, the mean curve was digitised to capture the shape of the curve, 17 points were used.
Continue reading Fan controlled by humidity sensor – design technique

Fan controlled by humidity sensor

I have a problem with machine tools getting condensation on them when conditions in the shed read dew point.

A possible solution being explored is to circulate air with a fan, possible inducting outside air, when humidity approaches condensing conditions.

A quick search reveals the HDS10 resistive humidity sensor for a dollar or so on eBay.

Above is the HDS10 humidity sensor.

Most low cost humidity sensors use a humidity dependent capacitive element, the HDS10 is different in being a humidity dependent capacitive element and is therefore simpler to use with microcontrollers with ADC input.

HDS10-02

The above graph is from the datasheet. It is intended primarily for sensing high humidity (dew point, condensing conditions) which suits this application.
Continue reading Fan controlled by humidity sensor

U-BLOX LEA-6T GPS module – for experiments

This article documents a LEA-6T module build for general experiments.

The LEA-6T is an inexpensive GPS module (~$40 at time of purchase, but getting cheaper) that can supply raw pseudo range data.

LEA-6T02

The module above is supplied for use on UAVs of various kinds, and came complete with a plastic radome and cables to suit an APM copter. The module also contains a 3D compass (magnetometer) which is not used here.

LEA-6T03

Above is the internals of the module with a custom cable to pick up just the RS232-TTL signals from the GPS (and supply 5V). The connector is a 8pin Hirose DF13. Continue reading U-BLOX LEA-6T GPS module – for experiments

Atten APS3005S – a better thermostatic fan control

The Atten APS3005S is a 0-30V 5A linear DC power supply.

Atten-hcctl00

This later model includes a thermostatically controlled fan which at moderately light currents short cycles (10s on 20s off) and is very annoying… especially since it sits above my desk.

This project describes application of the generic heating / cooling controller (hcctl) to control the fan, reducing the short cycling nuisance.
Continue reading Atten APS3005S – a better thermostatic fan control

Micro SD card premature failure

I bought a couple of ‘generic’ micro SD cards on eBay about a year ago. They were not much cheaper than brand name cards, and though only speed 6 rated, were available locally for quick delivery. I have a vague recollection that it might have been a RPi product supplied with NOOBS on it (I have a couple of SD adapters with the RPi logo on them).

IMG_1599

These were both used in RPi B systems and worked without fault for the last year, though they are not running full time (perhaps a couple of hundred hours of use).

During a Raspbian sofware update, both cards failed with the same problem, they effectively became read-only cards. Continue reading Micro SD card premature failure

Chinese counterfeiters at it again – EZP2013

Some while ago I purchased a EZP2013 device programmer on eBay.

EZO2013

There were literally scores of sellers, and they all looked the same, and some variation in price from about US$25 to US$50… which is not unusual.

I used the thing a few times, and it was clearly a very poor product so I replaced it with a SOFI SP-8B which cost close to US$50 on Aliexpress including a bunch of (6) adapters. Continue reading Chinese counterfeiters at it again – EZP2013