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Full time power for Hess Truck display case.

Discussion in 'Power Electronics' started by Bird11, Dec 28, 2019.

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  1. Bird11

    Bird11

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    Dec 28, 2019
    Hello I am looking for advice on how to have constant power to a battery powered Hess Truck. I was asked to make a display case for a collection of Hess Trucks and to provide power on a switch to turn the trucks on when desired in their display case. I have little to no experience with this type of electrical work and wonder if it is even possible. Thanks ahead of time for any advice you can give.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
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    Nov 17, 2011
    Welcome to EP.

    Sounds rather simple:
    1. Find the nominal battery voltage for each truck. If these trucks are powered by e.g. AA batteries, the required power supply is (number of batteries)×1.5 V (as each battery has 1.5 V nominal voltage).
    2. Find the required current for each truck. Unfortunately that information is usually not available in the manual of this kind of toy. If you have access to an amperemeter (or multimeter with current measurement range) you can simply measure the current drawn from a set of fresh batteries and add 50 % safety margin.
      I take it from your question that you probably do not have such a tool. So it is guesswork how much power is required by your trucks. Tell us which kind of battery the trucks use - if possible with information how long a set of fresh batteries lasts, From that time we can estimate the current draw. Otherwise, battery size can be used as an indicator for current draw in a very coarse manner.
    3. You then have to get a power supply that has the same nominal output voltage as noted in step #1 and the same or a higher current rating as noted in step #2.
      You can use either one power supply per truck or a single power supply (only if the nominal voltages are all the same) or multiple power supplies, one for each nominal voltage. The output current of each power supply must be equal or be higher than the sum of the currents drawn by all trucks attached to each power supply.
    4. Connect wires from th epower supply (supplies) to the battery contacts of the trucks. Insert a switch into the power supply to each individual truck to turn power to that truck on or off.
      If you don't want to mess around with the trucks themselves (as you probably don't want to do as these seem to be collectible items) you can use battery dummies (link e.g. here) to make the electrical connection from the power supply to the truck.
    upload_2019-12-28_18-7-49.png
     
    Martaine2005 likes this.
  3. Martaine2005

    Martaine2005

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    May 12, 2015
    Hi Bird11, @Harald Kapp gave you some excellent advice as he usually does.
    I have a couple of questions which may make this a little trickier....
    The 2019 tow truck has over 65 LEDs, different sound generators, working tow ramps with hydraulic sounds etc....
    The sounds and lights are operated by seperate switches on the tow truck itself. They look like tactile switches going to a toys circuit board.

    [​IMG]
    Do all these have to function too and have access to them?.
    Lastly, does the display case rotate?

    Martin
     
  4. Bird11

    Bird11

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    Dec 28, 2019
    Thanks gentlemen,
    To start with, the batteries are two “C” batteries that is a common factor on all the trucks and I can either borrow the tester I need or just insert new batteries and time how long it can stay on till they are dead. I believe that can work right? As for the control functions of the trucks themselves, I was asked for the lights only. They will be displayed and will not have easy access to them. As I am a cabinet maker I did not feel I could provide rotation and a power supply to the trucks since my knowledge of electric and circuits is almost non existent. That would be an added bonus if I could give them that function. One other thing, each truck has mini vehicles with lights ( 2-a76 batteries) that come with the trucks themselves which would also be displayed with the trucks. Looking to minimize the amount of power supplies while leaving room for additional acquisitions.

    thanks for all your advice guys
    Bird11
     
  5. Martaine2005

    Martaine2005

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    May 12, 2015
    Hi, each vehicle has 3 volts via two C batteries. How many vehicles are on display at the same time?.
    I would guess that the batteries would last about 2 hours of constant use. Guessing by my children's toys with lights etc......
    I am sure the toy manufacturers have a good deal with battery manufacturers..:p.
    The overall process is still pretty simple though...As explained by @Harald Kapp above.
    If you want to have the display rotate, the use of a slip ring is required.
    [​IMG]
    [​IMG]
    As for the small trucks being towed or on the flat beds, they would also be wired in the same way as the larger trucks. Or simply added to the larger trucks connections.
    If the display case is very large, you could put each truck on it's own slip ring. That would look rather nice.
    Yes, putting fresh batteries in one and leaving the lights on would give an approx time for current draw. As soon as the flash rate and/or LEDs dim, that'll be it.

    Martin
     
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  6. Bird11

    Bird11

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    Dec 28, 2019
    Thanks Martin, the photos help me visualize what you are talking about. At the moment there are twenty items for display plus 1-2 minis per truck. I just realized rotation will take up a lot of room so I think I will have to scale back to a linear cubby style display case. Thanks for you advice. If you ever need carpentry advice please ask, it’s al I know......so far. :)
     
  7. Martaine2005

    Martaine2005

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    May 12, 2015
    Thanks Bird..... I am also a cabinet maker..:D
    Rotating each truck is a kin to it's size on a plate. A lazy Susan for example.
    [​IMG]
    But if space is at a premium, and the trucks are displayed offset to one another, that'll look nice too. Just a little thought though.. If all the trucks have blazing bright LEDs and are all in close proximity, maybe taming the beasts might be in order. I'd be interested to see if the circuit boards work off a lower voltage like 1 C battery (1.5v).
    Do you think you could insert 1xC battery and short the other terminals with a piece of wire? And see if it works at all or the LEDs are dimmer?. It may be advantageous to have them dimmer if they are all on at the same time.. Just a thought.

    Martin
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    That makes for 3 V.
    The tester is a more accurate method. When you borrow it, let you be shown how to use it to measure current.

    If all trucks are in one cabinet and all have that 3 V power supply, you need to buy a 3 V DC power supply with a current rating that is at least the same or exceeds the sum of the currents for all trucks.
    For example:
    1 Truck draws 100 mA (just an arbitrary number)
    10 trucks to be displayed
    -> total current 10×100 mA = 1000 mA = 1 A
    Your power supply would be rated 1 A or higher. Do not worry about a higher amps rating: the trucks will draw only as much current as they need. So for example if you were to find a 2 A power supply that would be fine for the above example.

    The a76 batteries are 1.5 V, too. So two of them also make 3 V. The same power supply can be used. You'll need a different type of battery dummy.
    By the way: you can buy of the shelf dummy batteries in almost any size. E.g. for C-cells like these (that page is in German, sorry, but you'll surely find comparable products in your country.
    For the A76 batteries I haven't found off the shelf dummies. But you can build one easily. My guess is the 2 batteries are in series which makes for this construction:
    upload_2019-12-29_14-34-4.png
    You can use the same technique to build your own C cell dummies.
     
    Martaine2005 likes this.
  9. Martaine2005

    Martaine2005

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    May 12, 2015
    Actually, I just read up on these little collectibles.
    Is the display going to have older trucks in it too?
    The older trucks have incandescent mini bulbs and can draw 600-800mA. So in an ideal world, you would need to measure the current draw from each truck.

    Martin
     
  10. Bird11

    Bird11

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    Dec 28, 2019
     
  11. Bird11

    Bird11

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    Dec 28, 2019
    They are all newer trucks at the present. So for now all the advice is sound. Thanks harald I can find the appropriate page in English. Lol.
     
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