How do I use an op-amp in a new Bit design?

I think it looks great @chris101 feel free to submit and we’ll get back to you with feedback asap.

Thanks @syedBits! I am on track to do just that. I hope to have time to work out the remaining logic issues over the next couple of weeks, as school is out from today until June 1.

That’s awesome Chris!

I think I found it: op-amp nirvana!

I just got several OPA4342 op-amp chips. They are regular, “through hole” DIP style chips, so they will work on a breadboard, chip-sockets, or solder them into perf-board. Single (or dual) supply, +5 volts and ground work just fine. It’s a 14 pin quad package, with the same pinout as the popular LM324, so you can just drop it into an existing circuit.

Oh, did I mention that they are RAIL TO RAIL!!!

Here is the datasheet. I just tested them, they work as expected: 0.0v to 5.0v.

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@chris101, do you know if a 4 pin rail to rail op amp? I really like 4 pin chips.

Hey @JackANDJude - the 4342 is the only single supply, rail to rail opamp in a DIP through hole package I have been able to directly purchase. But after I found them, I quit looking. There are a lot of choices of dual and single chips though. Here is a list from digikey (I have not bought from them, but hey are referenced at aruino forum a lot):

http://www.digikey.com/product-search/en?vendor=0&keywords=opamp+dip+rail

I had a chance to look through that list, and this one looks good:

http://www.digikey.com/product-detail/en/MCP6241-E%2FP/MCP6241-E%2FP-ND/683249

It doesn’t hurt that it’s made just down the street from where I live either. :smile:

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I never found the Microchip device, but I came across these op amps from Adafruit:

TLV2462, Rail to Rail input and output, 80ma, 2.7-6v, 6.4MHz op-amp

2462s are dual amp chips should be good for building new littleBits projects. I just ordered a few, so I’ll let you-all know how they work.

(By the way, I’m still liking the 4342s - I used them is this and this project., but these TI chips are are smaller and cheaper when a circuit only needs 2 amplifiers.)

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Did you try the TLV2462 yet, @chris101? I had bought the LV321 SMD, but the truth is I much prefer through hole. :wink:

Hello @JackANDJude, hello @chris101,

I used the TLV2462 on my breadboard bit. It works quite ok. However, when I tried to use it as an inverting amplifier, it starts to swing under certain conditions. I haven’t had the time to investigate this further.
Currently I only use it as a buffer in the voltage follower configuration.

Thanks @SeventhDwarf! I ordered some - really looking forward to a 5v output. :zap: :stuck_out_tongue_closed_eyes:

@SeventhDwarf, I see you’ve used this already - your breadboard bit ROCKS! When you play with the oscillation, please post about it. Although I rarely use an inverting amplifier in these kind of circuits. I have an instrument amplifier in mind, so it would be important.

Hiya @JackANDJude!

I bought 4 of them a few weeks ago, but haven’t used them in a circuit yet. (“Soon, soon”, I keep telling myself.) You will get 5V out - at least into a high impedance load like a littleBits circuit (or an arduino pin …) Here’s my test setup, compared to a “regular” 741 op amp:

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@chunte,

Chris, @chris101, perfectly illustrates in the video above why I need to change op amps in my tilt trigger design. It’s still on my to do list, and I’ll get started making a tutorial as soon as I get the new chips. :wink:

Thanks, @chris101!!!

Success! Thanks for sharing your chip info @chris101 @SeventhDwarf & @codewizard58!

On the top is the version 2 tilt trigger with two 741 chips, resulting in a signal output of 4.4 volts. On the bottom is version 3 with one TLV2462 chip, outputting 5.0 volts. :smile: I’m so excited!

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Excellent work Jude, and I like the resistor bands on your schematic! :smile:

On the schematic, on the signal line on the left, between the 0.1uf cap, and the -I don’t know what value (I’m colorblind) - resistor, there is a symbol I don’t recognize. Is it a tilt switch?

Thanks, @chris101! Between that cap and the 1M resistor is a drawing of a ball tilt switch. I’ll be sure to keep color blindness in mind and label the resistor values before I publish. :wink: I wanted to film a tutorial this weekend, but I think it will be better with a perf bit than bit snaps on a random perf board. :grinning:

Making progress… :slight_smile:

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Hi Jude @JackANDJude,

I studied your diagram but I cannot figger out what it should do. I see a tilt switch and an oscillator or am I wrong?
One small remark:
I think it is a Littlebit standard to keep the SIG impedance appr 1 MegOhm.
Then I think the 1MegOhm resistor on the left side in your diagram should be connected directly to the SIG connection and not via the tilt switch… :scream:
Now the SIG line is floating when the tilt switch is open or not ?

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Hi @alexpikkert! That weird thing on the left is a drawing of a tilt switch, then an inverter because the 555 is triggered by a negative pulse, then the 555 as a one shot, then back to a second op amp to bring the voltage back to 5v. This circuit worked well on the breadboard, but I need to troubleshoot the soldered version to get it working.

Basically, when the ball tilt is tilted correctly, the 555 sends out a steady 5v signal for a couple seconds to smooth out the bouncing around of the ball inside the tilt switch.

Regarding the placement of the 1MegOhm resistor, I modeled the placement after the button and roller switch. What do you think?

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It’s a ‘bit’ gangly, but certainly more bit-like than the breadboard. Very nice design, especially considering how many components you have and the small size of the perf bit.

The use of your op-amps as comparators is very cool. That should make it capable of handling a wide range of input levels . If you put a dimmer on the input signal, then you should be able to turn it down so that it does not detect tilt with a low voltage in, right?

On the state of the input, perhaps an LED on the input would help determine if the input is floating. When it’s triggering, the LED should light. and go off when the switch is open. If it flickers, then the line is floating.

All in all, it’s a very neat device!

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