[GreenKeys] Model 14 keyboard adjustment

Wed Aug 9 23:01:00 EDT 2023

 Eric--If you are using an ordinary ohmmeter to measure the contact resistance of your keyboard contacts, be aware that usually these sorts of meters put out only a few mA of current in the resistance measurement mode. You need to have a sufficient sealing current through these types of contacts. If you want to measure the contact resistance, apply your 60 mA current loop through the keyboard contacts and measure the voltage across the closed contact(s).  Using Ohm's law, deduce what the resistance is. From a practical standpoint, your measured voltage should be significantly less than 0.5 V
Also, under no circumstances please do not apply any solder to the contact surfaces to build up the "thickness" since this will likely permanently ruin the contacts and will only last a very short while. In this application, solder is worse than useless as a contact material.
I hope that the above helps you in getting your 14 in tip-top shape. You are to be admired for embarking on this educational journey.
73, George W6BN
    On Wednesday, August 9, 2023 at 07:22:53 PM PDT, Eric Moore <mooreericnyc at gmail.com> wrote:  

 See attached slow-mo video, I hand cranked and cleaned, but resistance is still high. I almost want to tin the contacts with solder.
I have been using contact cleaner, perhaps I should move to metal polish? I was told it may do a better job removing surface oxides, or maybe I should go at it with some fine sandpaper...
-Eric

On Sat, Aug 5, 2023, 8:45 PM Mike Douglas <deramp5113 at yahoo.com> wrote:

If this is an R, you should see two high periods of about 22ms within the character frame. These high periods occur when those bit position switches close, but you’re only getting a brief spike at the instant those switches close and open. You need to work on those contacts more. Hand crank the keyboard through the bits and verify closed resistance on each bit/switch position is an ohm or less.

Mike

> On Aug 5, 2023, at 7:32 PM, Eric Moore <mooreericnyc at gmail.com> wrote:
> 
> Hello all!
> 
> I am working on my 14s keyboard. I have attached a photo and a trace from my scope. 
> 
> It looks like it is bouncing? Any ideas how to improve the signal? This is R, so 01010
> 
> Thank you for any help! I have my printer kinda working, I am going to use the keyboard to dial in the timing on the governed motor.
> 
> -Eric
> <20230805_190327.jpg>
> <20230721_121647.jpg>
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