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I have built the following circuit -

enter image description here

first, I soldered together all the mt3608 components on PCB and tested it (I created DIY voltage step up module), then using jumper wires I connected the battery module to the circuit and the Peltier.

The circuit is designed to deliver 6.6V to the peltier, without the load (the Peltier), it does its job successfully (V7,8=6.6V), but, after connecting the Peltier, I measure only 1.7V (and 300mA) on pins 7 to 8 (voltage drop on the Peltier module).

Why does that happen and how can I get the Peltier to be fed with the original output of the converter of 6v?

Datasheets- mt3608 - https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf Peltier - https://peltiermodules.com/peltier.datasheet/TEC1-12706.pdf

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    \$\begingroup\$ what's a tp4056 doing in between? \$\endgroup\$ Jun 25, 2019 at 10:01
  • \$\begingroup\$ Some of the components apparently cannot handle more current than the 300mA you're measuring. For what current is the inductor rated? \$\endgroup\$
    – JimmyB
    Jun 25, 2019 at 10:06

1 Answer 1

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Facts: -

  • The TP4056 can supply up to 1 amp at up to 4.2 volts
  • The MT3608 starts to hit the end-stops when supplying currents of about 1 amp
  • The Peltier module has a resistance of about 2 ohms

Why does that happen and how can I get the Peltier to be fed with the original output of the converter of 6v?

So, any voltage across the peltier greater than about 2 volts will result in the TP4056 and MT3608 being unable to supply enough current. Either or both will cause a problem.

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  • \$\begingroup\$ I'm confused, the tp4056 is only for battery charging, not discharging, so the 1A max current is for input only and doesn't affect discharge. Second, the mt3608 is capable of handling more than 1A according to datasheet. \$\endgroup\$
    – Danaro
    Jun 27, 2019 at 15:00
  • \$\begingroup\$ I'm confused why you are confused. \$\endgroup\$
    – Andy aka
    Jun 27, 2019 at 15:01

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