Have you ever wanted a second set of sense switches?

[Roger Meier]

Here is your solution :-)

https://github.com/rogermeier/Altair8800-IOBus-Cards/tree/main/11-sense-switch-input

[Chris Davis]

Very cool!  Nice to see other designs for expansion cards.

[John Kennedy]

I have to wonder - what interesting problem were you keen to solve with this? 

[M M]

Interested in the original thought as well but for me, I put a 5v level shifter daughterboard on it and use it for a "ttl input card"

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[Roger Meier]

There wasn't a specific problem, really. But this seemed like a useful thing to add to the casual hardware hacking toolkit.

Anytime you need to be able to easily input more than one 8-bit value for whatever reason this can be useful.

One of the times this has come in handy was when I was testing assembly code to perform a multiplication of two signed 8-bit integers. One of these cards plus the sense switches on the Altair plus two LED output registers or David's Bus Monitor card to display the 16-bit result as two 8-bit values makes it an easy task.

And, as was also pointed out, this can be a simple TTL input card if the handshake signals is not something you need. It's cheaper to build than the Parallel Port card (especially if you don't populate the switches), and it uses commonly available ICs. Sourcing the Intel 8212 for the Parallel Port card can be tricky and pricey. It also consumes less power.

So, the original thought was simply "Hey, something like this could probably be useful", so I went ahead and made it :-)

[Roger Meier]

Thanks!

I also have an ESP32 card in the works. The layout is done, but I haven't built it yet. The current tariff situation makes making boards with PCBWay or JLCPCB a lot more expensive that it needs to be. So, I've put it on the shelf for the moment.

On Tuesday, July 28, 2026 at 5:22:21 AM UTC-7 famousd...@gmail.com wrote:

[Tom Lake]

When I submitted the Gerbers, BOM and Pick&Place files to JCLPCB, it came up with an error although it didn't tell me what line the error was on.
Has anyone had a fab house make this?

[Chris Davis]

>>  The current tariff situation makes making boards with PCBWay or JLCPCB a lot more expensive

If you order less than 1.5kg and select Global Standard Direct shipping from JLCPCB, you don't pay tariffs.  You can order five of these boards for $5.12 shipped your door.

[Chris Davis]

>> When I submitted the Gerbers, BOM and Pick&Place files to JCLPCB, it came up with an error

The BOM and CPL files do not appear to be in JLCPCB format.

[Chris Davis]

Here you go I had ChatGPT convert them to JLCPCB format.  You'll need to select the parts since the CPL files does not have LCSC part numbers.

[Roger Meier]

I ordered the bare boards from PCBWay built it myself. I bought the parts on Digikey. Here is the Digikey BOM: https://www.digikey.com/en/mylists/list/8MC6P9T4RA

I also have a few extra bare boards left: https://www.ebay.com/itm/167768791137

[Roger Meier]

The BOM and CPL files do not appear to be in JLCPCB format.

Correct. They are whatever format KiCAD spits out by default. 

[Roger Meier]

If you order less than 1.5kg and select Global Standard Direct shipping from JLCPCB, you don't pay tariffs.  You can order five of these boards for $5.12 shipped your door.

Good to know!  Have you tried this recently?  I have had it happen in the past where I thought I was getting cheap shipping only to get a request for payment from the shipper later to get the shipment released from customs.

 

[Chris Davis]

Good to know!  Have you tried this recently?  I have had it happen in the past where I thought I was getting cheap shipping only to get a request for payment from the shipper later to get the shipment released from customs.

I just received one a few weeks ago and I have one on the way.  I order a couple times a month. 

[Roger Meier]

Excellent! Thanks!

Roger

On Jul 29, 2026, at 7:25 PM, Chris Davis <famousd...@gmail.com> wrote:



Good to know!  Have you tried this recently?  I have had it happen in the past where I thought I was getting cheap shipping only to get a request for payment from the shipper later to get the shipment released from customs.

I just received one a few weeks ago and I have one on the way.  I order a couple times a month. 

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[Chris Davis]

I keep a spreadsheet of all my orders.  Just for fun I compared the average delivery times from JLCPCB based on carrier (production time included):

FedEx: 10 days

UPS: 11 days

Global Standard Direct: 14 days