Shop OBEX P1 Docs P2 Docs Learn Events
Spec'd at 3.3V, could greater be applied to power a prop? — Parallax Forums

Spec'd at 3.3V, could greater be applied to power a prop?

dusgdusg Posts: 3
in Propeller 1
Say +5V or more?

Comments

  • RaymanRayman Posts: 15,289
    Don't do it! You'll fry the pll first and then other things...

    You can input 5V signals though by using a series resistor, like 10k-Ohms, in between 5V and Prop pin..
  • jmgjmg Posts: 15,193
    dusg wrote: »
    Spec'd at 3.3V, could greater be applied to power a prop? Say +5V or more?

    Sure, provided you do that via a suitable 3v3 regulator. Linear and switching regulators are available to >> 5V.

  • dusgdusg Posts: 3
    Thanks Rayman :)

  • MacTuxLinMacTuxLin Posts: 821
    dusg wrote: »
    Say +5V or more?

    If you could spare a little cash/pcb real estate, take a look at voltage translators
    e.g. https://www.ti.com/lit/ds/symlink/txb0104.pdf
  • Toby SeckshundToby Seckshund Posts: 2,027
    By intention, I ran a 40 pin DIP P1 at 4.2 Volts for an experiment. This was because I had dreams of bolting a real Z80 to it - and 4.2 V was about half way between the 3.3 and 5 V ... nothing horrible
    seemed to happen, but it was obviously "all at my risk". It also seemed a crude experiment to see if a single Li-Po cell could get used.

    Unintentionally - I ONCE picked up a 9V PSU lead, rather than the 3,3V one. That did not go well ... (SD card still worked, after it cooled down)

    I see that there are little Buck/boost 1.8 V - 5 V to 3.3 V things (cap charge thingies I think) that would seem good for that - not sure if they would like the 100mA (ish) that a P1 running VGA etc ...
  • kwinnkwinn Posts: 8,697
    edited 2020-01-01 16:51
    Toby Seckshund wrote: »
    By intention, I ran a 40 pin DIP P1 at 4.2 Volts for an experiment. This was because I had dreams of bolting a real Z80 to it - and 4.2 V was about half way between the 3.3 and 5 V ... nothing horrible
    seemed to happen, but it was obviously "all at my risk". It also seemed a crude experiment to see if a single Li-Po cell could get used.

    One might get away with using a single LiPo to power a Prop directly but charging it "in circuit" might be a problem unless an LDO regulator is added between the Prop and the battery. Connecting a real Z80 to the Prop has been done several times IIRC, and should be relatively simple. The CMOS versions can operate over a relatively wide voltage range.
    Unintentionally - I ONCE picked up a 9V PSU lead, rather than the 3,3V one. That did not go well ... (SD card still worked, after it cooled down)

    I see that there are little Buck/boost 1.8 V - 5 V to 3.3 V things (cap charge thingies I think) that would seem good for that - not sure if they would like the 100mA (ish) that a P1 running VGA etc ...

    If you are referring to the capacitor based voltage multipliers/inverters based on charge pumping that are typically used to provide low currents at higher and/or +- voltages for things like RS232, op amps, comparators, etc. then no, they will not be able to provide the currents required. A proper buck/boost switching regulator is what you need. I'm pretty sure a Prop and Z80 could run directly from a single LiPo.
  • localrogerlocalroger Posts: 3,452
    Actually the Prop has a very wide range of current usage, and in the right application -- low power, slow clock, not a lot of cogs in use -- it probably could run from a buck/boost circuit. I know we tend to concentrate on what it's doing when we push the performance envelope (102 MHz, eight cogs doing fourier transforms and VGA) but there's also RCslow with modest I/O and wake up to quickly do stuff once in awhile before the capacitor bleeds off.

    This is one of the neat things about P1 which will not be true of P2.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2020-01-01 22:27
    Check out the Semtech SC630. It outputs 3.3V ±3% at up to 400 mA continuous, with inputs ranging from 2.9V to 5.5V, using only small switched caps -- no inductors -- and an internal LDO. Output ripple is held to 20mV P-P.

    For powering the Prop from a battery, consider lithium 3V primary cells (e.g. CR123A). They're not rechargeable, but have a high energy density and can be purchased in bulk for a reasonable price. Combined with the SC630, you'd get a true 3.3V.

    -Phil

    Edit: Corrected part number to SC630.
  • PublisonPublison Posts: 12,366
    Phil Pilgrim (PhiPi) wrote: »
    Check out the Semtech SE630. It outputs 3.3V ±3% at up to 400 mA continuous, with inputs ranging from 2.9V to 5.5V, using only small switched caps -- no inductors -- and an internal LDO. Output ripple is held to 20mV P-P.

    For powering the Prop from a battery, consider lithium 3V primary cells (e.g. CR123A). They're not rechargeable, but have a high energy density and can be purchased in bulk for a reasonable price. Combined with the SE630, you'd get a true 3.3V.

    -Phil

    That's a hard part to find. Do you have a link?
  • Peter JakackiPeter Jakacki Posts: 10,193
    Publison wrote: »
    Phil Pilgrim (PhiPi) wrote: »
    Check out the Semtech SE630. It outputs 3.3V ±3% at up to 400 mA continuous, with inputs ranging from 2.9V to 5.5V, using only small switched caps -- no inductors -- and an internal LDO. Output ripple is held to 20mV P-P.

    For powering the Prop from a battery, consider lithium 3V primary cells (e.g. CR123A). They're not rechargeable, but have a high energy density and can be purchased in bulk for a reasonable price. Combined with the SE630, you'd get a true 3.3V.

    -Phil

    That's a hard part to find. Do you have a link?

    Try SC630

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    Right you are Peter, thanks. I've corrected my original post.

    -Phil
  • PublisonPublison Posts: 12,366
    Thanks Peter.
    Nice device Phil. Thanks.
  • Toby SeckshundToby Seckshund Posts: 2,027
    https://www.amazon.co.uk/ARCELI-1-8V-5V-Power-Supply-Module/dp/B07MY2BS2K/ref=sr_1_1?keywords=3.3v+buck+boost+regulator&qid=1579200161&sr=8-1

    Was what I was thinking about. I haven't seen any firm data (as if it would be entirely true) about current capabilities, other than it is supposed to be happy with a ESP8266 hanging off it ...but does keep on repeating Low Power this ... that ...
Sign In or Register to comment.