# Speed Calculation / RPM with Dashbox

**URL:** <https://forum.realdash.net/t/speed-calculation-rpm-with-dashbox/395>\
**Category:** SPLeinonen\
**Created:** [March 25, 2020, 12:37pm UTC](https://forum.realdash.net/t/speed-calculation-rpm-with-dashbox/395 "2020-03-25T12:37:07Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Clubsport](https://forum.realdash.net/letter_avatar_proxy/v4/letter/c/0ea827/32.png) [@Clubsport](https://forum.realdash.net/u/Clubsport)\
**Post date:** [March 25, 2020, 12:37pm UTC](https://forum.realdash.net/t/speed-calculation-rpm-with-dashbox/395/1 "2020-03-25T12:37:07Z")

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Hey guys,

in a project, I’m thinking About using Dashbox from SPLeinonen.  
I’m missing a few digital Inputs, but I think analog Inputs will also work and to the Transition to 0/1 in RealDash.  
Due to the fact it’s an old car, I wonder how to do the calculation for Speed (i just have a speedpulse source) and RPM (number of ignition pulses) ? ❓💡

Would be great if you can give me an idea… ![:mrgreen:](https://forum.realdash.net/uploads/default/original/1X/683e6e6bb670bc005ee53129f28bd708e4eae697.gif "Mr. Green")

Kind regards,  
Martin

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**Author:** ![SPLeinonen](https://forum.realdash.net/letter_avatar_proxy/v4/letter/s/e9c0ed/32.png) [@SPLeinonen](https://forum.realdash.net/u/SPLeinonen)\
**Post date:** [March 25, 2020, 3:24pm UTC](https://forum.realdash.net/t/speed-calculation-rpm-with-dashbox/395/2 "2020-03-25T15:24:13Z")

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Hi Martin,

Analog inputs work just in the way you describe. There is 2pcs 0-18V inputs and those are good also for +12V.

Are You able to use GPS? It’s been quite popular and it is also accurate. What kind of speedpulse source You have? Is it VR or Hall type sensor? I have been thinking to do converter inside box what read VR sensor pulses for speed but it’s here yet…

Best Regards  
SPLeinonen

> [@](#):
>
> Hey guys,
> 
> in a project, I’m thinking About using Dashbox from SPLeinonen.  
> I’m missing a few digital Inputs, but I think analog Inputs will also work and to the Transition to 0/1 in RealDash.  
> Due to the fact it’s an old car, I wonder how to do the calculation for Speed (i just have a speedpulse source) and RPM (number of ignition pulses) ? ❓💡
> 
> Would be great if you can give me an idea… ![:mrgreen:](https://forum.realdash.net/uploads/default/original/1X/683e6e6bb670bc005ee53129f28bd708e4eae697.gif "Mr. Green")
> 
> Kind regards,  
> Martin

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<div class="post-metadata">

**Author:** ![Clubsport](https://forum.realdash.net/letter_avatar_proxy/v4/letter/c/0ea827/32.png) [@Clubsport](https://forum.realdash.net/u/Clubsport)\
**Post date:** [March 25, 2020, 6:50pm UTC](https://forum.realdash.net/t/speed-calculation-rpm-with-dashbox/395/3 "2020-03-25T18:50:00Z")

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The analog inputs will not be a problem i think, maybe if I need more with 18V I can do a conversion to 5V externally.  
Speedpulse source I will check!

GPS not possible unfortunately, the tablet has none and USB is blocked for charging… 😒  
And I didn’t find a way to use the Fire HD8 in dual charging and OTG mode.

Just checking my options ATM, building an Arduino to RealDash-CAN-Device would be possible, but using Dashbox much easier!

Kind regards,

Martin