Re:Re:Show us your homemade Test Equipment

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28 Feb 2021 18:44 - 28 Feb 2021 19:07 #47125 by Wightscope
Show us your homemade Test Equipment was created by Wightscope
This was mentioned in the Rotkee vs Pico thread recently.
I've made quiet a few sensors and get good results.

Some very useful ideas to be found on "gadgets playlist" on YT, I got the stethoscope idea from there.
With a piezo sensor and the range of cheap pressure transducers off ebay (£13/$15) I get some decent results, you just need to build a stable 5v supply - which I did before realizing it would be much easier to use a cheap phone powerpack as they have 5v USB :)

L-->R, COP sensor, exhaust/intake pressure pulse, stethoscope, 5v supply with an in-cylinder sensor on it - It's also used for fuel pressure with a 100psi sensor, I cut/welded an injector and did in-cylinder on a diesel, cut/welded an HO2S with a 15psi for exhaust back pressure.



Diesel in cylinder (this was a 1000psi sensor so resolution not so good)



Exhaust pulse V8 Jaaag

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Last edit: 28 Feb 2021 19:07 by Wightscope. Reason: Making Tyler happy
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28 Feb 2021 19:03 #47126 by Tyler
Replied by Tyler on topic Show us your homemade Sensors
Can we open up the discussion to include homemade test equipment in general?

'Cause I got a gem here :lol: - my homemade DLC BOB:



Yes, I drilled the holes by eye. Yes, that's Gorilla Glue holding the voltmeter in place.
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28 Feb 2021 19:09 #47127 by Wightscope
Replied by Wightscope on topic Show us your homemade Sensors
Test Equipment - done!

That is brilliant, must have been in a hurry for it! :P

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05 Mar 2021 18:04 #47245 by stevieturbo
Replied by stevieturbo on topic Show us your homemade Sensors
Not mine, but one that could be useful and is very cheap to do as the code etc is freely available.
A crank/cam signal generator based on an Arduino nano where you can output various crank/cam signals ( square wave....don't think it offers VR ) and at varying rpm's

The intention of it isn't really universal diagnostics, as it's targeted to a specific project, but obviously it can have generic uses too.

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05 Mar 2021 19:06 #47247 by Tutti57
Replied by Tutti57 on topic Re:Show us your homemade Sensors
I'm working on a little nerd project that I'll share at some point. It's probably not going to be as cool as I imagine...

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08 Mar 2021 14:20 - 08 Mar 2021 14:21 #47310 by Noah
Replied by Noah on topic Re:Show us your homemade Sensors
Banana jack test light!Works with all my back probes, piercing probes, alligators and spade connectors. Plus it plugs right into my Power Probe extension lead and Power Probe cigarette lighter adapter, making it super easy to have a good ground or battery feed anywhere you are in the car.



-Seems to me that I could live my life, a lot better than I think I am.
I guess that's why call me The Working Man.-
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08 Mar 2021 14:29 - 08 Mar 2021 14:43 #47312 by Noah
Replied by Noah on topic Show us your homemade Test Equipment

I'm really happy with the Nissan Altima refrigerant pressure sensor used as an in cylinder transducer too.
It just has a USB connector I plug right into the Verus USB port for a 5v power supply.

-Seems to me that I could live my life, a lot better than I think I am.
I guess that's why call me The Working Man.-
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09 Mar 2021 20:24 #47338 by Tyler
Replied by Tyler on topic Show us your homemade Test Equipment
First up, my MVP for parasitic drain testing:



Then there's the less used Pico drain tester. Only comes out when I want to measure draw overnight or longer:



The classic exhaust leak pressure tester! Gauge doesn't work anymore. :blush:



My go-to for COP secondary waveforms. Guts of a Honda distributor, some Amazon cable and Digikey ends.



Last but not least, my test lights! Moe and Joe. Moe got sucked into a fan blade awhile back, hence the mid-coil repair.

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10 Mar 2021 03:16 #47344 by Wightscope
Replied by Wightscope on topic Show us your homemade Test Equipment
Like the vice grip earth. I saw that Eric O does that, seems like a good mod. Looks like you do a lot of parasitic drain testing!

@Noah always been a bit wary of connecting any of my home made stuff to a USB port, but that refrigerant sensor looks good.
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10 Mar 2021 03:21 #47345 by stevieturbo
Replied by stevieturbo on topic Show us your homemade Test Equipment
You can buy cheap 12v to 5v adapters, I'd prefer to use that than attach stuff to the laptop usb ports. Plus while testing some stuff off an Arduino plugged into my home pc, it seemed to be only 4.7v. won't matter for overall trace, but for absolute readings it would matter.
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10 Mar 2021 18:08 #47357 by Tyler
Replied by Tyler on topic Show us your homemade Test Equipment

Like the vice grip earth. I saw that Eric O does that, seems like a good mod. Looks like you do a lot of parasitic drain testing!


Oh I blatantly stole the vice grip thing from SMA. :silly: After doing that, I can't go back to normal test light clips.

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12 Mar 2021 19:32 - 12 Mar 2021 19:34 #47400 by Wightscope
Replied by Wightscope on topic Show us your homemade Test Equipment
Like the parking sensor, sensors. What about RF key fobs?
Following an incident today where the fob was showing a transmission on the key fob tester, but as we later found out (post wild goose chase) was transmitting garbage, any ideas for a cheap sensor 315/433.93MHz that would do the trick for a scope... Or I guess I could just pick up a used RF antenna or two
Last edit: 12 Mar 2021 19:34 by Wightscope.

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13 Mar 2021 09:25 - 13 Mar 2021 09:36 #47429 by Wightscope
Replied by Wightscope on topic Show us your homemade Test Equipment
Doing a bit of research on this. Please correct if I am wrong!

Unlock fobs transmit in response to button push on 315/433Mhz, so far so easy, - get an used antenna for $10 and provide it with power. Watch on scope - in the example mentioned above when the key was tested with an RF tester it was transmitting, but scoping the LIN output from the RF antenna with the button pushed there was a drop of 0.5v, on lock and nothing on unlock, rather than transmission of code 0-12v

The Keyless entry systems/ Passive entry have low frequency transmitters 125-140kHz on the outside of the car in the doorhandles, this effectively acts as a digital finger on the fob so the fob transmits the unlock signal and the car unlocks when the handle is touched.

Keyless start uses the same LF antennas but only inside the car, the key then responds with either an IR or RF broadcast - same frequency as unlock, picked up by same Rf antenna?

In the slot fobs I assume just use the usual transponder technology

So 2 RF antennas 315Mhz and 433Mhz and a 125-140kHz detector for outside should do it.?
Last edit: 13 Mar 2021 09:36 by Wightscope.

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17 Mar 2021 17:33 - 17 Mar 2021 17:33 #47539 by Wightscope
Replied by Wightscope on topic Show us your homemade Test Equipment
Right so bought the first antenna I came across on eBay , looks just like ones I have seen before, it's off a 2012 Vauxhall (GM) Astra. However when it arrived it's got 4 wires. All the info I have is for 3 wires. I am assuming it's just an extra ground.
Does not appear to be any info available on it - typical! Before I give in and buy another one does anyone have a plug out for similar?

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Last edit: 17 Mar 2021 17:33 by Wightscope.

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25 Mar 2021 11:47 - 25 Mar 2021 17:10 #47766 by Wightscope
Replied by Wightscope on topic Show us your homemade Test Equipment
Pfff, well that didn't work. Got a 3 wire Volvo receiver instead. Fed it 12v and E, expected a LIN signal on key transmission and ... nada. Just sits at 4v.
Maybe my theory about any receiver working with any key was wrong.
Unless the lin signal needs to be pulled to high or low at the other end to work.. EDIT Bit of swotting seems to indicate that I need to add a pull up resistor and a diode.
Last edit: 25 Mar 2021 17:10 by Wightscope.

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27 Mar 2021 14:12 #47828 by Wightscope
Replied by Wightscope on topic Show us your homemade Test Equipment
Nope, 30kohm pull up on the signal wire, I can see a brief what looks like a self test signal output, but nothing on a key signal.

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27 Mar 2021 18:59 #47839 by Matt T
Replied by Matt T on topic Show us your homemade Test Equipment
Those antennas might not do anything unless they receive a signal from a paired remote. Wonder if a software defined radio would be able to grab the signal? They're pretty cheap.

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