Solid construction, elegant design and high precision production. Once upon a time, Hewlett Packard Testing and measurement tools that were dear to the working engineers. Sure, leave one of those infants on your foot and you were watching a broken toe. But this is a small price to pay for reliability and some character building. So when I recently came in the early 1970s Himachal Pradesh The 7041a XY recorder while cleaning his parents’ attic, I knew that I just wanted to see if I could lift it up and run again.

What is the difference between a XY recorder and a plotter?

XY recorder Unlike the plotter, in real time, the data was designed to chart data from analog instruments, which plots the output of the digital computer. Basics are the same: there is a mechanism to lift and reduce a pen, and Motors To move the pen to a page surface. The big difference is that a plotter usually uses a digital command to control the speed of the pen, while the speed of a recorder’s pen is controlled by analog voltage input.

So I just needed to do that the HP recorder had to feed the right voltage, and I could attract what I wanted! Only a few obstacles were standing in my way.

Recorder allows interface Python Code is written on one Rasbhari pie [bottom right] To create analog signals which are transferred up and down to the level to complete the various categories required by X-and Y-Axis of the plotter. James provost

The first obstacle was getting the house, because my parents were attacked Ireland And 13 kg, 48-by-36-by-17-saint meter was not fit to fit my suitcase back to NYC. In the packing material and shipping fees, the US $ 300 solved that problem, and I was still a little ahead of the game financially compared to getting a uniform vintage recorder EbayAnd the way before purchasing a new Banom tool Nextdro plotter With a similar drawing area. (To be fair for the bantam, its plotter is sleek plug-and-play devices that can handle a very wide range of pen).

The second obstacle was that the recorder did not work. Once I took it home, I came to know that y-Xis can be adjusted manually using a knob on the control room, but X-Axis was dead. The mechanism of lifting and reducing the pen created a weak clinking sound and barely added to the twisted.

“Did I spend a lot of money to send just an HP-model boat anchor home?”

I opened the case, which was a quick task with a Philips screwdriver – no strange safety screws, no glue, no delicate plastic, no yellow sticker warns that your warranty will be zero and if you dare to look inside you will probably be boiled. Beautifully excluded Printed circuit board Inside, I saw something Resistance These were not clearly part of the factory installation. Was they amendment or repair? If the latter, were they successful or did I spend a lot of money to send just an HP-model boat anchor home? And I did not know how the 40-Pin interface connector behind the recorder should have been tilted to control the signals.

All these problems were solved when I found a recorder manual on eBay. Oh, what a manual. Not only the operation instructions, but also to completely separate the recorder and keep it back together. It lists every component, with photo Circuit board And electronic schemes on gatefolds. And this included the direction -guidelines to modify the circuitry if you wanted to measure various voltage range compared to the factory settings – remove a inhibitor Here And There And mix in some new people. This explained the resistance I saw. In a world where license and software lock Only refuse people by plugging in a replacement componentThought of a major company that is encouraging its customers to break Tank Iron Mind is bogling.

Connected: Why should we fight for the right to repair our electronics

Soon, some application Instrumental oil, Silicon greeceAnd Kimwips Was X-Axis and pen lifters are working again. I tilted a variable power supply for the connector of the recorder and slowly Bring the voltage up as I saw the pen holder in response. This allowed me to determine the input range of the recorder, which left for 0 to 1 volt y-Axis, and 0 to 5th X-Xis, covering 25 and 38 cm speed respectively, with about 0.2 mm accuracy.

The next step was to build an interface. Although Microcontrollers Often digital-to-analog capabilities are built-in, often only a true analog output pin. I needed two. Like a technique pulse width modulation Lets me output an analog on several pin, but usually with Only 8-bit resolution Or 256 separate voltage levels. I needed at least 1,900 levels to match the accuracy of the recorder.

The raspberry pie uses an expansion “hat” and two 12-bit digital-to-analog converters that have been commanded to create a 3.3-volt control signals through I2C connectors. These are transferred from 0– V and 0- to 5-V range using voltage dividers and amplifiers respectively, as well as a logic gate used to change the 3.3-V digital signal that increases and reduces the pen to 5-V levels.James provost

So i bought two $ 5 Adafruit Mcp4725 breakout boardThese 12-bit digital-to-analog converters are-each provides 4,096 different levels-controlled on one. I2C serial Connection, and two boards can share the same I2C bus. I associated them with A Raspberry Pie Model B+ I get out of a drawer via $ 6.60 Sparkfun Quvic Hat,

DACS gave an indication in the range of 0 to 3.3 V, so I sent a board output through one Voltage divider To scale it from 0 to 1 V y-Axis. For X-Axis, I fed other board output through one LMC6484 Amplifier, powered by a 5-V pin from PI, does not have a full range to bring it from 0 to 4.8 V, but will do it until I come with a more sophisticated interface. I brought a signal to the pen to lift and reduce the pen, which comes out of the PI’s GPIO PIN, passes it through one 74LS08 and Gate IC A cheap and cheap 3.3- to 5-V is used as a digital level shifter.

I then wrote the code on the PI, in which the Plotter was written through its pace, using parametric equations written. Circuitpithon Wandering Hypotrokeoids And other geometric curves. Ultimately, it should be possible to accept the PI and translate commands written in a plotter-control language. Hp-gLThen i will be able to conspiracy to the vector Graphics And lessons like drawing software InkscapeBut for now, I am happy that my recorder should be hummed next to me, hail and made to heart and last.